He is empowered to make treaties with the advice and consent of the Senate, not to tell a bunch of penniless con artists that he'll hand them $5 billion dollars. Bush doesn't have that authority unless he's talking about his own money. I doubt he has that kind of money, myself.
Oh, the subject you raised, not the subject of the article. ok
As for {{giving}} aid being Constitutional, I don't know, never thought about. But either way, our voluntary gifts or loans to other nations and our club dues to the UN are NOT taxes. Lecture over.