The basic problem here is that these plans mis-consider the US as an isolated economy. If you have basic income, what is the policy on immigrants? The options appear to be:
1. Open immigration and same benefits to everyone. Maybe you can argue that we can afford basic income for current US citizens, I think it would be a stretch for anyone to argue that we could afford it for anyone that comes into our borders, and thus...
2. Get even more hard line against immigration. America is already pretty anti-immigration, just wait how opinions turn when anyone inside gets a guaranteed income. As usual, anti-immigration laws will hurt the next round of brilliant foreigners from coming to the US and bringing their great ideas and prosperity here. Its already the case that we're increasingly lending foreigners our education system and then not letting them stay and thus exporting that knowledge and prosperity.
3. Make basic income only available to US citizens. Congratulations, we have now fully devolved into a classist society, where an 18 year old that wants to "figure things out" will be granted a monthly salary, but an immigrant who has 3 kids won't. To make matters worse, they probably WILL pay taxes on their income that will go for said basic income. Arguably we have this partially now, but since its services its not as unfair as giving a check to someone by birthright while the other person has to labor. For all the talk of automation the reality on the streets today is that immigrants largely do our back braking labor, and if you now "buy out" all Americans from menial jobs, you are cementing that these tasks are for outsiders.
Milton Friedman put it best: you can't have open immigration and a welfare state. We already see the effects of our current system hurting immigration. These proposals always have the ring of "post history" to them: we've figured out supply, now its time to just find out how to split up the goods. I think they greatly underestimate that the world economy is still not figured out and we could soon find the US behind other states.