The posters in this thread attributing the "military spending" to America's military "power" and finding some kind of correlation between the two
are completely unequivocably WRONG.
The REASON the U.S. spends so much on their military is because most of their stuff simply COSTS FAR MORE than the equivalent things in other
countries due to cheaper labor. I.E. in Russia a sophisticated fighter jet will cost something like 5-15 million USD. In America the same level of
fighter jets cost 100 million or more EACH. The reason being that the scientists, laborers, and engineers in Russia for example that are making these
products are making 1/4 of the wages that their American counterparts are making. Thus in short, countries like China and Russia are able to arm
themselves with weaponry just as sophisticated as that of their American counterparts but for 1/10th of the price.
Now don't get me wrong even if it weren't for this discrepancy in labor costs the U.S. would still probably be spending more on defense budgets $
than any other country but just NOT as ridiculously more like they are doing now.
So in short, no the U.S. absolutely would not be able to take over even ONE country such as Russia, China, or North Korea let alone the entire world
that is laughable and absurd to even suggest.
The U.S. got its butt whooped in Vietnam, has done very poorly in Afghanistan and Iraq and is unable to even maintain control of cities there as
someone else mentioned. There is no way the U.S. would make ANY ground in an actual invasion or ground war against ANY major military power such as
North Korea, China, Russia, etc. And if you disclude "conventional warfare" then U.S. loses even worse in that case because other countries have far
more unconventional warfare weapons than the U.S.
For example, Russia has not only the biggest stockpile of biological weapons in the world (far more even than the U.S. and almost every other major
country COMBINED) but Russia also has far more nukes than the u.s.
Just take a look at this article and list and see for yourself
if an all out nuclear/biological war broke out guess what country would be left standing last? That's right Russia not us, because Russia has 1. far
more landmass and thus there will still be inhabitable parts unlike the U.S. which would be a total wasteland and 2. Russia has far more nukes.
So, in conclusion your answer is no, the U.S. could not conquer the world even if it used every single weapon in its arsenal.