Wether you call it defence or offence, the US has never done anything without having something to gain. Even though the US lacks history, the history of its support to some groups and suddenly cutting relationship with these, is certainly getting back ten-fold now. Too many shortterm decisions, and too few longterm. But I guess nothing wins an election, like a good old war
I know that the US has always fought its wars with an objective. Thats the point of wars. And the US is notorious for being isolationist up until the end of WW2, when the US found itself as one of two superpowers. Then the sudden switch to having a massive responsiblity caused alot of bad blood which still is around. Not to mention jealosy.