The modern world is different from the past in many ways, such as NATO, the UN, nukes, vast international trade, rapid communications, power moving away from the church and aristocracy, and horror at the vast death toll of the world wars. I couldn't imagine Canada invading the US if the Canadians suddenly developed an unstoppable superweapon, and even if the US became completely isolationist I doubt Germany would invade France again any time soon. The west has too much trade, too much communication, too much tourism to want to fight even if NATO, the UN, the EU all shut down.

On the other hand, the fact that the US gave Germany money for rebuilding in the immediate aftermath of WWII really is an unprecedented act of generosity.