Medlling in the affairs of rising powers, specifically seeking to deny the empire of Japan access to needed resources and thus control their actions, is what caused the sneak attack on Pearl and in effect caused The Two. Recall that Germany declared war on us 4 days after Pearl, we didn't declare war on themWhy is it only Europe's problem? (I agree that they should be participating, and they are.)
[Because it directly affects their security in many ways, some of them subtle]
When does it become USA's problem?
[Never]
Honestly, the "it's Europe's problem" sounds like the late 1930's isolationist rhetoric. That turned out well.
We were quite strongly isolationist as a people, but isolationist beliefs didn't cause The Two. It took a cowardly sneak attack on one of our primary naval bases to change that, done by a country that calculated we would not allow them to achieve the empire they desired and that the drastic weakening of our sea power would allow Imperial Japan to take what they wanted and the time to consolidate it