It's not that they're powerful, but the problem is how they use said power. They use said power to try and install friendly regimes to them around the world so that they can keep their power. The issue here is that it more often than not goes bad once the people find out. As examples, Iran, Al'quaeda, Cuba, Libya.
So, overall, the USA is not too powerful, but they use their power wrongly worldwide for quite a bit of the time, and unfortunately it doesn't only bite them back in the ass, it bites others too.