If only one country provides UBI to immigrants, that country will see a rise in immigration. At what point do taxes raised from the new residents exceed the money paid out?

Or maybe you're talking about UBI to immigrants, but not actually allowing any immigration.

I don't know what immigrants mean here. Like migrant workers or illegal immigrants?

Otherwise, we are a country full of immigrants who have become citizens or legal residents and would benefit from UBI.

Immigrants means anyone in the US that isn’t a citizen.

Legal residents would not get UBI until they become citizens.

Why wouldn't we allow legal residents to receive it?

Politics mainly. It's already hard to convince people to give up part of their wealth for their fellow citizens. Good luck convincing them to give it up for non-citizens.

Also, logistics. If immigrants can get the UBI, then people would flood in from all over the world just to get UBI. You'd either have a ton of expense, or you'd have to make legal immigration nearly impossible.

It would certainly be challenging to be a non-citizen resident if you have to pay the same taxes as everyone else, but are cut out of such a major benefit.

Basically a gigantic extra tax for not having citizenship.

Without the right to vote, I think it would be hard to get much political will for it. Even if we started out giving it to noncitizens, it would be the first thing cut in budget cuts.

Doesn't that happen in the US already? Farm work, hotel cleaning, groundskeeping... all heavily reliant upon immigrant labor.

Yes. Which is why the UBI wouldn't make nearly as much difference as people think. Nearly all the "work people don't want to do" is already done by immigrants who won't qualify for UBI (but would still be paying the VAT taxes that fund it).

That's basically how the math works out. Immigrants fund a lot of the UBI by paying into it but not benefiting from it. We would need a lot of protections for non-citizen workers to protect them from being exploited.

To be clear, I'm a big fan of UBI and think it's a great idea, I just worry about the unintended consequences.