Yes, Everster, I can confirm what you are saying about American school structure.
I went to a school that had six dormitories, 3 boys, 3 girls. They definitely had personalities and strong character traits. We also had 'Dorm Wars.' These were humorous prank battles. They usually got out of hand at some point during the year and the school would have to step in and shut us down. Pranks included things like stealing the drying machine doors, filling the hallways with paper cups full of water, and covering the windows with shaving cream. You get the idea.
One boy's dorm would ally with one girl's dorm at the beginning of the year. They were expected to do nice things for the girl's dorm in order to 'win their favor.' Roses, chocolate, serenades.... Sometime another boy's dorm would crash the party with buckets of water/hoses.
Freshmen were assigned dorms, but after that they were free to choose. Students tended to gravitate towards their friends, hence each dorm's personality. Not everyone was passionate about dorm rivalry, but enough were to make things get interesting.
So yeah, I always understood Hogwarts house loyalty, even though I am an American. And I have lots of Notre Dame friends-- what you say there is true.
I think this would all carry over into an American school of magic.