...and despite the swipe... I will add a bit more.

After every war we have had an upcoming social upheaval. After WWII, though not really well documented, there was large groups of dissatisfaction with the world and with the ideologies and religions that consented, even in absentia of dissent, the circumstances that brought about WWII.

The Oppenheimer's were out there in multitudes in academia and communism was flirted with by many. Sci-fi fans here should know about the Futurians (circa 1945) of sci-fi writers/editors who were often openly or covertly sympathetic to Marxism or communism. And these influential writers and groups had a HUGE impact on general belief systems.

The first world war gave birth to the riotous roaring twenties, excess and indulgence. It was an open rebellion to the Victorian age and it's belief system. The roar died down during the depression as a wake up call and the depression opened the door to fundamentally alter the US system to a quasi-socialistic affair.
Hungry mouths have no problem offering a bit of freedom for food. This same philosophy always empowers the would-be dictators and Chavez in Venezuala is only one of hundreds of examples throughout history where the poor masses have been riled to reform or overthrow an existing government.

As Raoul alludes to above, Europe rejected religion and war. The longstanding political ties between France and Russia during czarist times opened up France to the whole communist thing in spades, however many Frenchmen were burned when Stalin initially cozied up to Hitler - against France - and so that's the only reason France didn't go full tilt communistic, but stalled at high socialism instead.

This cultural influence from Europe has always been found among the US wealthy east coast folks and subsequently was also incorporated into our Ivy league universities - and from there contaminated all academia. After 1945 Ivy leaguers were taught that nationalism was evil. That had NEVER appeared in US schools until after WWII. It had been hinted at during the New York World's Fair of 1939-40, before the US was involved in yet another nationalistic European mess, in the "Court of Nations" where nations paraded their products and goods and where the Soviet Union made sure they had the tallest building in the court.

So WWII brought about today's current, as Tom so colorfully put it, "cr-- where you live" ideology in the West which was taught in schools and now has watered all the way down into the elementary school classrooms.

This doesn't exist in the East, mainly because they have NO academia to speak of, and where they do they are not influenced at all by European thought.

So while as you suggest, beneficial aspects to the anti-nationalistic meme, I'm reminded of Kirk and Spock in City on the Edge of Forever:

Kirk: "Edith was right, Peace was the answer!"

Spock: "But at the wrong time. Her influence delays US entry into the second world war, allows Germany to complete her heavy water experiments, develop the bomb first and with their V2 rockets captures the world."

Here's the most important thing the US needs to remember:

It's pefectly fine for other nations with their inferior constitutions, lack of freedoms and controlling governments to be anti-nationalistic, but as the standard bearer of freedom, democracy and personal freedoms - the USA does not yet deserve, much less afford such a self-loathing attitude. What's worse, if we continue down this path the whole world will fall back into a series of dicatatorships, fundamentalist hellholes and totalitarian regimes as the one true "good guy" stands down.