I recently read an article by a Dutch UBI pundit who changed his mind and came to the conclusion that a 'real' UBI is unreasonable, but that a negative income tax might be a good way to achieve the goals of UBI: a basic level of security for everyone. It would cost around €4-€5 billion over here, which is not insanely high compared to the €6 billion subsidies for fossil fuel and €14 billion in mortgage interest deduction our government already spends.
Five billion euros for 17 million people is a hundred billion euros for 300 million people. It's also $300 a year which means the actual money comes from somewhere else. Mess around in here. I jacked taxes to the absolute max and managed to free up a trillion dollars by 2040... that's $2500 each, or double (and some) the Alaska dividend. Let's give that to only the 20 percent of the US population taking any sort of government benefit and yes - we're effectively doubling their available money. But make no mistake: we're talking about welfare, not UBI. We aren't doing any radical experiments. I mean, in most of the world you get 100% your salary for a quarter of a year just for having a kid. Realistically speaking the US would blow through that surplus I created just instituting modern paid family leave.