Interestingly, now that the Evil Empire has devolved into a mob-mediated mess, our enemy de jour seems to be OURselves (thank you Pogo?); the increasing polarization of American politics and cries of "TRAITOR!" hitting the airwaves (Screw you, Ann Coulter) is a utterly unhelpful sort of introspection.
Actually, the successor to the Kaiser helped us finish off our old enemy, England. Roosevelt (the other Roosevelt who also ran our navy) drove a hard bargain with lend/lease and like programs ultimately forcing the British to give up her colonies after that second great European conflict of the twentieth century. And we vanquished the Krupp Empire as well in that conflict. Unfortunately, our current enemy is a nameless, faceless nobody, unless you count Osama Bin Laden although I am sure they will come up with another leader of our current enemy in due course.