Suppose immigrants from Somalia make the US a better place in the long term – more vibrancy, richer tapestry, spicier salad bowl, whatever, it works out in the long term.
First, we never get to the long term. After the Somalis it’ll be the Congolese, then the Uighurs, then, who knows? the Latvians, or the Hutus, the Mancunians, the Savoyards.
Second, the long term benefits accrue to the Somalis, and to the upper class. The short term costs are born by those racists at the bottom who can’t live in a gated community and send their child to private school.
It’s part of a larger pattern. The people in charge make policy regardless of what the rest of us want, externalizing the cost of that policy while capturing the benefit. Then they condemn us as bitter clingers, racists, and resentful older brothers.