It's the general level of brashness and inconsideration that astounds people from other nationalities. Silly offensive jokes expressed in the loudest way possible, not caring about the reaction of others, etc. These things lead to alienation naturally.

Anecdata: a group of 10-12 Dutch tourists have gathered on a central table in a dinner bar, all laughing as loud as possible without ever considering a mom with a sleeping baby a few meters from them. The mom tries to make facial expressions of discontent, no one gets it or no one considers it some kind of a sign.