I think US immigration should be "Everyone except for terrorists is accepted".
I would be a bit more discerning than that, tbh. Rapists, Pedophiles, Embezzlers, Thieves, Murderers. I don't want people like that either. No reason to increase their numbers.
And you have to throttle it. History shows us that mass migrations usually leads to massive upswings in violence and crime especially among the lower economic classes. Even before the mass migrations that come at sword point.
Further, when a person immigrates, he or she brings a piece of their culture or politics. If you aren't careful you can import things that are currently bad.
Female genital mutilation, for instance, is AFAIK a pretty common practice in parts of Africa. If you aren't careful you will create a bloc of people for whom to be able to circumcise girls is important. And because DEMOCRACY!!!!1!!!!!!one!!! If that bloc is big enough, it could become socially acceptable circumcise girls by the now majority.
Or enough non-terrorist but devout Muslims from say Iran or Yemen (Countries where LGBTQ+ activities are criminalized up to the death penalty) and the Anti-LGBTQ+ bloc could become very, uh, bad. And powerful enough to vote in people to make it worse and worse for LGBTQ+ people.
Perhaps enough Chinese CCP people come to the USA or anywhere EU and they flood the voting blocs and then it becomes the will of the people to submit to the CCP as vassals.
If you are Socialist of any stripe, having positive immigration control is critical because you need to know how many people to give welfare/whatever you call it to. So you can predict and provide needed supplies to parts of society in the command part of your market. Or worse, you could bring in a capitalist! Enough of those and socialism goes down the drain.
Or you could be Texan and the flood of Californians are already making it difficult to be a small business owner with the heavy business taxes they voted for (and fled from).
Like there's no situation where, without a world wide government and world wide quality of life average at the very least, you don't want to have positive control of immigration.