re: Amazingly, American Football is not in Europe... why?

I agree with two of your reasons. The third sounds like some SJW crapola. If boorishness and bad behavior was a detriment, the hooliganism of soccer, especially British soccer would have doomed it. Not to lay all the blame on the Brits as there have been incidents all over Europe of such behavior. Out of control fans aren't an American monopoly; there are riots at cricket matches (!) in India for example and Aussie rules fans can be very outrageous.

The principal reason is cost. It's much cheaper to train kids in sports like soccer, basketball and even baseball than to start with peweee football then move on up.

And finally the stop and go nature doesn't appeal to people that like the continuous action of soccer, rugby, basketball, hockey, etc.