The argument that “there were always immigrants in this country and they all assimilated perfectly well” really gets my goat.
“Always” is actually while the nation-state was strong and offered appealing narratives to integrate oneself into.
“We are a land of freedom where anybody can achieve anything through hard work” is an appealing narrative.
“We are racist bastards who are the worst evildoers in history and we hate ourselves and our past” is not an appealing narrative.
The economic system in the US is still very attractive but the American identity is not. So don’t tell me people will integrate. You have dismantled your history, erased your past, and are wailing about how horrible you are. There’s nothing to integrate into.