You are right Blue, there are some who did not fit in very well. Maybe most? wBut, aside from the Amish, the groups you name are very traditional "American". I would not that, in dealing with the Mormons, it was congress who passed a constitional law defining marriage as the union between one man and one woman. Emphasis then being on the "one" rather than "man" or "women". I think it was the Edmunds-Tucker Act.
Maybe the melting pot was just a goal, rather than a reality in the past. A warm fuzzy ideal which we all thought was worthy. It no longer seems like much of a goal for anyone today. It is Right wing nuts, or Left wing loons. Black, white, Christian, atheist, Jew, Muslim. . . Hyphen American, not American plus more.
I think we are better as a whole, even if that means I have to put up with Blue's wrong opinion.