The strongest economic argument against immigration is the claim that immigrants free-ride on government-provided goods. There’s a lot to say about this claim; here I limit myself to one point.
The goods and services that people complain immigrants cause to be overused are either government-supplied goods and services (for example, government schools) or goods and services that are heavily subsidized by government (for example, medical care). No one complains that immigrants are over-using supermarkets, movie theaters, auto dealerships, or clothing stores. That is, private enterprise seems quite able to ‘absorb’ immigrants and prevent overcrowding and free-riding. Problems arise almost exclusively with goods and services supplied or subsidized by government.
I understand that on pure utilitarian grounds it’s too simplistic to say "Oh, the solution is for government to stop supplying these things." Given that government is supplying or heavily subsidizing X, Y, and Z, and given that immigrants can use X, Y, and Z, problems are indeed created.
The narrow cost-benefit solution might well be further restrictions on immigration — I say "might," not "is" — even if, in my opinion, such restrictions are unethical because they violate the basic human rights of Americans and foreigners alike.
But even if we conclude that, on pure cost-benefit grounds, the best course of action is to restrict immigration further because immigrants overuse public-supplied and subsidized goods and services, why blame immigrants? Why point accusing fingers at immigrants? Why not blame government for supplying and subsidizing things that it ought not supply and subsidize?
The root problem is not immigration; it is government provision and subsidization of goods and services that should be supplied by the market.