I was born, raised, and educated in the USA, and I never heard this "U.S. Defender of Freedom" thing. We stayed out of WWII because large portions of the US wanted to avoid a repeat of WWI, just as the Oxford Student Debating Society solemnly resolved that there was no reason whatsoever to die for King Or Country just a year or two before Churchill and Co. shamed poor Chamberlain into demanding that Germany not invade Poland or suffer Britain's (and France's) wrath. After Japan attacked, we might have known that Germany needed to be included in the war but Germany was nice enough to declare war on us, before we had to try to convince Congress to declare war on a previously non-belligerent power just because we didn't like them.
We did not declare war on the Vichy regime because we thought that nominal neutrality might work better (and we decided to treat them as if they were the Ghetto Councils that the Nazis set up before they liquidated the Ghettos, ie in charge like Holly Genarro in Die Hard). We "knew" about the death camps, but no one believed the reports because they were made by commy-symps and Jews, and the idea of killing your best and smartest workers was too absurd, just as the Red Cross was notified of the Katryn Forest massacre of Polish officers by the Soviets, but they didn't believe it because the Germans reported it.
Face it, pre-emptive war, even against a righteous target, has lost a bit of its luster in the last decade. If the USA *did* decide to do something about NK, large portions of the world, including Europe, would complain about US Cowboy Diplomacy and Warmongering.
BTW, would Poland have objected so much if the Germans asked them to join in a crusade against the Godless Communists on their Eastern border, instead of what happened?