To start with, assessing relative military strength based on relative levels of military spending is a lot like betting on a race horse based on how much the horse eats. Sure, horses have to eat, but a horse that eats ten times more than all the other horses is probably not going to come out ahead because there is something seriously wrong with it.
Then consider the fact that a dollar spent on the US military in the US is not directly comparable to a dollar's worth of rubles or yuan spent on in Russia or China; in terms of purchasing parity, the ratios can be 5 to 1, or even 10 to 1. If Russia gets 10 times the bang for the buck, there goes the assumption of supposed US military superiority based on how much the US military eats.
Also, let's not lose track of the fact that the US military has different objectives from the rest of the world's militaries: its goal is primarily offensive rather than defensive. The US military strives to dominate and subjugate the entire planet; everyone else simply tries to defend their territory, while a few countries also try to thwart the US military in its ambition to dominate and subjugate the entire planet.
In general, if the objective is unrealistic, it doesn't matter how much money is wasted in trying to achieve it. More specifically, it's a lot cheaper to break something than to make something work, and the US military, no matter how much money is spent on it, remains quite cheap to neutralize. For instance, a Nimitz-class aircraft carrier costs somewhere around $5 billion, while a Russian Kaliber missile that can be launched from a fishing boat from 1200 km away and destroy it is competitively priced at $1.2 million apiece. To put these numbers in perspective, Russia can wipe out the entire US aircraft carrier fleet without exceeding its military training budget for the year.
But all of this matters only if the US actually spends money in trying to achieve some actual military objective. If the US military establishment mostly wastes its money on vanity projects and expensive technological albatrosses, then none of this matters at all, and this may very well be the case. Just look at what the US actually spends its defense dollars on:
• It spends it on military bases around the world—hundreds of them. What purpose do they serve? What does their presence achieve? Nobody knows. It's all part of US military “activity”: assessing and responding to “threats,” most of which are purely theoretical. It seems to have an irrational compulsion to not leave any spots on the planet without a US military base. This is mostly just a waste of resources.
• It spends it on a bunch of aircraft carrier groups. These are very useful for launching attacks on defenseless countries. But it is very important to keep these aircraft carriers outside of conflict zones that may involve China or Russia, or even Iran, because each of these countries has several cost-effective ways to destroy an aircraft carrier: ballistic missiles, supersonic cruise missiles and supersonic torpedoes. The entire aircraft carrier fleet is obsolete, and is another huge waste of money.
• It spends it on the Aegis integrated naval combat system, which is considered state-of-the-art and has been installed on a number of cruisers and destroyers. There is just one problem: it is trivial to shut down, as Russia has demonstrated. A jet fighter equipped with a basket of electronic countermeasures equipment called Khibiny was used to shut down Aegis. The jet (which was otherwise unarmed) then performed a dozen bombing runs on the defenseless US navy vessel.
• It spends it on disastrous development programs of various kinds. A classic example is Ronald Reagan's Strategic Defense Initiative, a.k.a. “Star Wars”: it never resulted in anything strategically useful. Another good example is the F-35 Joint Strike Fighter, which cost over a trillion dollars to develop. It is supposed to be useful for a lot of different missions, but has turned out to be ineffective for all of them.
This list can be continued virtually ad infinitum, but just these examples make clear a basic principle: spending money on things that don't work does not make the US any stronger militarily.
Next, look at the manner in which the US spends money on defense. It spends it by paying military contractors, which are public companies—highly profitable ones. These defense contractors are not primarily interested in delivering value in terms of defense spending; they are interested in generating profits for their shareholders. This is the stated prime directive of all public companies. Therefore, it is safe to write off a good third of all defense spending which goes toward profits: this money may feather a lot of nests, but none of that is military-related.
Also, keep in mind that much of the money is actually just pretty much stolen. The Pentagon has not been audited in decades, and sums unaccounted for run into the billions of dollars. A great deal of defense-related spending is recycled using a variety of schemes into campaign contributions for members of US Congress, whose members then unfailingly vote for increased defense spending. There is also the scheme where defense contractors pay exorbitant consulting fees to retired officers in what is really a form of deferred compensation: the officers work for the defense contractors throughout their careers, but are only paid after they retire. Nobody knows what fraction of defense spending gets siphoned off using these or any number of other corrupt schemes, but it seems likely that the US military establishment is the single largest den of corruption that this planet has ever seen.
The little bit of money that might eventually get spent on developing useful defense systems runs into a truly insurmountable problem: lack of brains. You see, for generations now the US has been falling behind in science and math, along with almost everything else. There are some excellent universities and institutes in the US that graduate top-notch technical specialists, but they mostly graduate foreigners. At the graduate level in science and engineering, US nationals are a small minority.
Now, this doesn't matter in many technical fields, where it is common practice in the US to hire foreign-born specialists. But defense is special: it requires native talent, or the allegiance, and the morale for doing superior work, simply isn't there. And so the defense contractors end up being staffed by native-born knuckle-draggers who couldn't get a job that wasn't defense-related. In turn, the Department of Defense is staffed by similarly dim bulbs: highly caffeinated fitness freaks who run around looking busy, waiting for their next promotion, never criticizing their superiors, never questioning their orders no matter how idiotic they are, and never thinking too hard. What can a system like that achieve? Disasters, that's what.
And so that's what we see: a long sequence of unmitigated military disasters. The US has been involved in a long series of military campaigns against very weak adversaries, in which it proved itself capable of destruction, with staggering levels of collateral damage, and some very impressive unintended consequences such as the emergence of ISIS/Daesh/Islamic Caliphate, but not much else.
Critically, it has turned out to be utterly incapable of winning the peace. The ultimate objective of all military missions is cessation of hostilities on favorable terms. If this objective cannot be achieved, then the military mission is worse than useless. Has the US military been able to achieve cessation of hostilities on favorable terms in any of the countries in which it intervened militarily—Afghanistan, Iraq, Libya, Yemen, Syria, the Ukraine? No, it certainly hasn't.
The US defense establishment can be considered victorious in one sense only: it has conquered and subdued the people of the United States, and is extracting a plentiful tribute from them. It is a pure parasite, serving no useful purpose. It should be disbanded. As far as standing up to the neighbors, the Texas National Guard should be a good match to Mexico's Federales in case Mexico decides to stage a military-style reconquista, which is unlikely, since the de facto demographic reconquista is going so well. On the other hand, the northern border requires no protection it all, since it is inconceivable that Canada would ever pose any sort of military threat.
Of course, there is an alternative to voluntarily disbanding the US military: a resounding, humiliating military defeat at the hands of clever, cost-conscious adversaries. However, this plan is fraught with the danger of triggering a nuclear exchange, and highly placed Americans who are concerned that a nuclear explosion might interfere with their personal longevity plans should give the voluntary approach a good think.
P.S. Some people might find my criticism and suggestions “unpatriotic” because we should all “support our troops.” Rest assured, this has nothing to do with the troops: they do not get to make procurement decisions, and they do not get to choose their missions. As far as as patriotism is concerned, it is the sworn patriotic duty of the troops to serve and protect the people, not the other way around. But if you wish to be a patriot, then you too can serve and protect the people, the troops in particular (because, don't you forget, they are people too) by bringing them home and giving them civilian jobs doing something useful, or at least something that isn't harmful to the world at large or to the country's finances, environment, health, reputation or security.