It's NOT a global tax. It's a decision your elected representative make to try and improve the geopolitical climate. I've always been a critic against much of our foreign aid. But if the funds are managed and distributed by the US in return for reasonable reform from those who get it, I'm all for it. It's nothing more than asking welfare recipients to do a little work for their check, which I'm in favor of.
Fine. Show me the grant of power in the Constitution which covers this. If you're going to claim it's covered in a treaty, show me which UN treaty requires foreign aid from the US and how much it requires.
I'll wait as long as it takes you to look it up.