Let's be fair. If you grow up in Bangledesh, Indonesia, or Brazil, you're not joining the U.S. Army for the sake of patriotism. You're joining it because you want something. In this case, it would be a very wealthy lifestyle, complete with free healthcare for you and your dependents, and a good shot at U.S. citizenship. That's not 'highest bidder' mercenary, but it's not exactly selfless service, either.
I've worked with some members of foreign militaries, and discovered that not only did I make more a month than their commander, I made more than their entire unit. Combined. Any one of those guys would be thrilled to be a soldier for the U.S. Army. Now, a great many of these people may become fine Americans one day, but let's call a spade a spade. To a guy in downtown Manila or the streets of Bombay, joining the U.S. Army is like winning the lottery.