"At some point the world needs to just agree to stop fighting over petty issues, like economics, religion, oil, ideology, tribalism, etc"
This is an oversimplification. The strongest counterpoint I can think of is what happened to the Netherlands in WWII. For similar reasons, to not send their sons to their deaths, to not destroy cities and lives in war, they ceded leadership to the Germans.
When their Jewish population was rounded up, it was too late to resist. By the end of the war, the population was in famine.
Infact, the whole rise of the third reich was in tandem with broken treaties and nobody willing to step in and stop the rising power until it was too late.
Some of these involvements are more nuianced. The actions against Saddam in Desert Storm might have immediately protected allies and other stable governments in the region, but allowing a genocidal despot to go unchecked may lead to much bigger problems in the future.
Many of these foreign interventions are to keep wars from reaching our doors. The recent example in Syria being the failure of involvement leading to millions of refugees on the doors of countries throughout the world.
I'm no war monger. War is utterly stupid. But if you're going to have a world where soverign nations are free to organize themselves, there will be situations where early intervention is needed, and those interventions may be very unsatisfying, inconclusive and politically self-defeating. It's hard to feel good about long, expensive, lethal protracted involvements on foreign soil for motives alien to your own forces, to achive the goal of preventing something not very specific from happening.
