Why have the Americans gone from taking a cautious approach to war to becoming a warmonger themselves? During the first and second world wars it took years before they entered the wars and then came Vietnam, Somalia, Gulf war one , Afghanistan and Gulf war two where all of them were started by the good old US of A were they not?
Don't make it so complex. We're petty and the first world war didn't directly involve us and we did enter the second after Pearl Harbor. Attack us, or something we need, like oil, and we're there.