I think Krugman misses the point of the World War II recovery.
The war era itself was a period of enforced austerity: on the home front we had rationing, victory gardens, and bond drives, and on the field the troops led lives of unimaginable austerity.
After the war, our economy took off because we had no competition - everybody else of any importance had their countries bombed all to hell. The Europeans didn’t recover from the war for decades - and then only with our help.
So it wasn’t the “common enemy” (alien or not) that brought us out of the war, it was the sacrifices inherent in fighting a war, and the economic advantages of winning one that were most responsible.
Now where’s my damn Nobel Prize?
Make that “brought us out of the depression”, not “out of the war”.
And if Carter, Gore, and Obama got one, as well as a pinhead like Krugman, I still say I deserve a Nobel.