'If your people are being subject to mass-genocide; that's different - we will help. But border wars, civil wars, insurgents, terrorists, whatever....do your own dirty work...stop getting others to do it for you.'
What about WW1 and WW2?America has never done that. Ever.
I am quite sure England and France asked for American help.
And America wisely stayed out of both (other then selling/lending them war stuff) until they had no choice.
And when she did - she suffered FAR less casualties, actually profited from the wars and her world position bacame FAR stronger as the result...while every other major power was weakened to some extent.