Because alcohol laws don't tend to get enforced unless there's a problem, because most of Southern Europe operates on a "village and neighboring villages" field of view and it would be socially uncouth.

Weed on the other hand is very strictly enforced for the most part, except in more touristy and "Americanized" places.

Smoking weed in Spain is legal since a couple of decades. Selling a small bag is illegal, but this isn't really enforced as it's hard to prove that the bag was for selling and not for self consuming.

Usually police will turn a blind eye both for selling pot and selling beer, unless anything goes wrong and somebody complains.

Is the illegalization (made up a word) of weed in Europe at all a USA export as well? Or did they come to it on their own?

Hard to say. The history is murky and involve a whole mess of international conventions.

https://en.wikipedia.org/wiki/Single_Convention_on_Narcotic_...

Seems to be the convention that brought cannabis into the fold.

An undercover cop could also bust them for selling beer.