Being a US citizen is inherently valuable. It gives the right to work in the richest major country. We can travel to much of the world visa free and very few countries want any harm to befall American citizens within their borders. The US has a very high standard of living and good infrastructure and its relatively easy for citizens to take advantage of that. Its not uniquely good. Being a British citizen or German citizen is comparable and better in some respects. But its better than being a citizen of many countries and so there are always a lot of people who want to immigrate to the US.
At the same time, there are a lot of US citizens who have trouble utilizing their status to its full potential. For a variety of reasons there are just 10-15% of the population that can’t seem to make it work. They have this great asset but its just not producing a return for them. So what would happen if we allowed these people (or anyone) to sell their citizenship. Imagine if the only way for a non-citizen to become a citizen was to buy another person’s citizenship. There would be millions of people who would be happy to do that.
Furthermore, lets imagine that instead of taxing citizens and then distributing that money to other (mostly) citizens in arcane ways, the US government taxed at the laffer max and then distributed most of that money as a “citizenship dividend.” That’s essentially a UBI but rather than setting its level and then seeing how crazy high taxes have to be, you set taxes to what will give the greatest NPV of revenue and pay out whatever you can from that. Like a corporation not a charity!
Combine those 2 ideas. The only ways to become a citizen or legally work in the US are either to be born a citizen or to buy a citizenship. Citizenships also pay a reasonably fat dividend (Got to be at least $5K/year if not more like $10K given current taxing and spending). How much would a citizenship be worth on the open market? Given the stability of the dividends, the impossibility of bankruptcy, and current low interest rates a multiple of 40-50 would be extremely reasonable. Plus some premium for the value of working in the US, and you can see how a citizenship could easily be worth $300-500K. Maybe more. Get rid of worldwide taxation and rich foreigners would buy them “for a rainy day.” Think about the value to low income people of being born with a $400K inheritance. It would be immense. That pays for college + a good start in the world.
Selling your citizenship would have to have consequences. You’d lose the right to vote. You’d lose the dividend but as long as you were born a citizen you should retain the right to live and work in the US and your kids (if born in the US) should still be citizens. We could pay out a decent dividend while still having a safety net for those who really need it so even if some unfortunate people sell their citizenship and then blow it on smack or whatever then they wouldn’t end up starving in the street. Real actual welfare for people who really need it is just not that expensive. To protect minors make it illegal to sell your citizenship before 18. That way parents can’t have kids as a way to get rich, though they would still get the dividend.
The total level of immigration might decrease, and particularly low skill immigration. But skilled workers would probably still be able to afford it. If they are going to be able to make a decent living, then they should be able to borrow to buy a citizenship. They can pay it off using the dividend + part of their earnings. It would be slightly painful but well worth it for smart people coming from poor countries, and of course their kids could get the massive benefit of being born citizens. More importantly, immigration would now be guaranteed to benefit American citizens since it would keep the value of their citizenship up, and would allow citizens in poverty the chance to escape.