BTW, the sinking of the Lusitania did not direcly result in the US entry into WW I, but that is a frequent assumption since most are not too up on WW I history 85 years later.
And in WWII we had to sacrifice the bulk of the Pacific fleet to get our pass to the fighting. In my line of thinking, I'd rather just jump in to help those fighting the good fight, than sacrifice human life & valuable materials.
The problem in WW II was who controlled the press... quite literally the bulk of the press was controlled by the liberals of the day, and socialists in particular. Moreso than today, the news press influenced American sentiment. It is likely that Roosevelt knew of the attack on Pearl Harbor, yet "allowed" it to unfold with little release of timely and accurate information to the pacific command, in particular Admiral Kimmel and General Short.
Even in retrospect, the "right" thing to do was to help stop the evils of the Nazis, Russians, and the Japanese. Italy is not included because as has always been true since the fall of the Roman Empire, the Italians were a joke, militarily... at least as a threat to world peace.
I agree that when the world sinks into war, America should act sooner rather than later... lives will be save in the long run.
Similarly, the US should have finished the Korean war in 1951, but a weak and cowardly President, for the first time in US Military history, put Americans under fire and directly caused their deaths, while denying them the abilty to fight the war militarily, or withdraw. Over 10 years later, we saw that mindset applied by another Democratic President.
Presidents need to learn the lessons taught by General George S. Patton, Jr., among others... namely that there comes a time when one must fight, and ask not about the short term daily casualties, but how many lives will be spared by ending the conflict. One of the worst Generals in American history, McClellan, taught this lesson to Abraham Lincoln in the American Civil Wat, too, BTW... but as a an negative example, vs. Patton's positive example.