I can think of 2 reasons: 1) For posturing. One reason others might not want to fight the US is the presence of a large and very well equipped force that appar

I can think of 2 reasons: 1) For posturing. One reason others might not want to fight the US is the presence of a large and very well equipped force that apparently trains for just such an eventuality. 2) The military-industrial complex is how the US economy stays ahead and yet pretends to be capitalist and free-market. If you pump domestic technology companies with trillions of dollars of tax money in the name of defence, they might just produce something valuable (say like the internet).