Sorry to disagree, but I do not view the US army to be the most powerful.
There are armies in other countries which are just as powerful, just as intelligent and probably have weapons to equal the US military. No-one knows for example what the Chinese have in the way of weapons but they can certainly match the USA in numbers and training. Not every battle however has been won by strength of numbers.
No doubt America could level Iraq and Afghanistan, however, the chances are that America would in turn suffer a dreadful retaliation from other super powers....
Never underestimate the power of others and never overestimate your own.