300,000,000 - US population
$12,000 - Your UBI amount
Total cost: 3.6 trillion dollars.
Projected US tax collection for 2019: 3.4 trillion. That’s not the US budget, just the amount not borrowed to pay for the budget.
Cost of social programs that UBI would replace (in theory): 2.3 trillion. (SS, Medicare, other). I don’t think UBI could replace SS though.
So you need to increase tax revenues about 33% if you look at it in the most favorable way.
Then, when the bottom falls out for those who needed the full benifit of the programs you replaced, you will either bring those programs back or increase the UBI payment for everyone, which is easy to do because we’d just vote ourselves more money, because money is free.