I always found it odd how restricted immigration is in the US, considering it's a country recently founded by immigrants.
The US is home to more migrants than any other country in the world. More than the next four countries combined. You should question why you believe the opposite of reality.
There is a reason Americans don't care about immigration from Canada but wanted to build a wall with moats, gun turrets and razor wire across the southern border.
For example, my family immigrated to South America from Italy 3 generations ago. I don't say I'm Italian and don't feel like an immigrant.
My point is that there has to be an extra force that keeps reminding them "this place is what it is and it was built by immigrants and we value that". If that exists or not in the US, I can't comment from the outside but without that core value being shared, people won't naturally think "oh, immigrants == good" (especially when illegal immigrants are being called refugees in some cases).
It does, there’s a pretty strong message in the US that it was built by and for immigrants. But it turns a large number of people have heard that and said “well now that we’re here, let’s close the gate”.
Similarly, you don't see much concern about illegal immigration from, say, South Korea, Singapore or Japan, or from rich middle eastern countries like Saudi Arabia or Dubai.
If you look for racism everywhere, you'll see it everywhere.