2 North American 4 You

Your first part is fair, but your second part is a bit misleading. We sent troops, just not until people were convinced that it was an "us" problem too. People didn't want to get tangled up in another one of Europes wars. Much like how most of the allies also didn't get involved until they got threatened too. Except the soviet's, who had an alliance with them.
It's not like providing the materials needed to actually survive is nothing. Our entire economy was repurposed around doing so. The repayment was because a massive "European problem" contingent thought a budget neutral requirement would keep us from helping. We worked out a system where we bought long term leases on land, and they used that cash to buy weapons from us. It was a shell game.

We got rich after the war because everyone else was rubble and we still had factories.