America will always fight wars because their interests in resources, political alliances, and ideological stability. It's for the money. It's always the money at the end.
America is the cultural and military hegemon due to the proliferation of free trade enforced through an unmatched navy. America becomes more powerful by maintaining this status quo. It's why dangers to the oil supply have driven 3 out of the 4 examples you rightfully point out. Sadly the Middle East is the oilbasket of the world with the worst borders ever designed. If you want energy, you spread influence there.
However, there is one instance where the interests of the USA align with the general interest of the average Westerner.
People don't like democracies getting invaded. And potential democratic trade partners getting invaded is bad for business. You can have both at the same time. I will not defend the Gulf War under this banner, but the faster that we can prove that land grabs are nonnegotiable in this Pax Americana, the better.
And also, you don't have to convince me that war is inefficient. I've read Catch-22. But you do have to convince me that the destabilization of the breadbasket of Europe (and the world) is less important than the opportunity cost of a couple million lost to a few hundred corrupt officials.