How do you think the US was founded? We are the strongest nation because we have the strongest military. Where would the US be without it's military? At best we could be Japan, but even they have their own military, and rely on ours to protect them.
Agreed, also because geography has thus far protected us from most major modern wars so we were able to avoid the catastrophic damage to infrastructure (and lives lost) that afflicted most of Europe and even Asia in WWII