Even if done completely right it is very expensive (like how the Scandinavians do it. Those countries have nationalized oil assets and small defense budgets, strict immigration.)
The US spends more per person on healthcare than any of the Scandinavian states - by a
substantial margin.
The Scandinavian states are a mixed bag when it comes to immigration - generally speaking they have higher rates of immigration per capita than the US, but lower shares of foreign born population. Mostly because of freedom of movement with Europe - other Europeans move there for a while, and then move elsewhere. Whereas once your in the US, that's pretty much it for most people.
And there is how we manage this country with semi open borders defacto open borders, granting citizenship to Dreamers etc. At our rate we would be paying for the health care of nut just ourselves but probably 1/3 of central American and south America .
Rubbish. "Semi open borders defacto open borders" is a fiction (also nonsensical).
The illegal immigrant population in the US is either static or declining. And has been so since about 2008. It's probably down by about 1.1 to 1.4 million on its mid 2000s peak.
The legal immigrant population in the US is climbing - mostly thanks to naturalisations - but the intake has been capped for five years now and the growth rate is slowing.
The biggest growth in immigration is
by temporary foreign labour. The number of temporary work visas for foreign nationals jumped massively in the past decade. In the second term of the Obama administration, temporary foreign worker numbers in the US grew by about 50%, to just over 2 million. By the second last year of the Trump administration (no data available for 2020), just under 3.2 million temporary workers were in the US.
The majority of these were for cheap(er) labour from China, India and Mexico. About 1/2 of them end up in four states: California, New York, Texas and Florida.
In a sense, the US has just replaced one source of cheap foreign labour (illegal immigrants), with another source of cheap foreign labour (legal immigrants on temporary work visas).