Why is this man being downvoted? He's correct. That is the historical reason America got involved.
There were tens of millions of Americans that supported the Germans/Nazi party, and the rest basically didn't want to get involved on the world stage again.
The real evils of the Nazi regime weren't realized until the last year or so of the war when we pushed in through the incursion areas and saw the camps and horrid treatment/deaths of the "undesirables". Then it became a true moral outrage that brokered no dissension. Until then, it was because we had 4billion+ in loans to Germany they were repaying us after our costs for WW1, among other financial incentives.
Claiming otherwise is whitewashing history.
America has never been a particularly great country. Don't let the school propaganda fool you. We've done things nearly as bad, and in some cases worse, than the Nazi party in our past. But nobody started a world war about it because we kept it within our borders (e.g. the Native American genocide, slavery, etc.).
I think the individual people who went to war from America in WW2 were doing the right thing, and believed in it for the right reasons. But the people at the top pulling the strings? Financial justifications all the way down.