taxing foreign aid, and international trade are two very different things.
You cant throw tax on government aid programs, because it would destroy the integrity of the program, not to mention the entire thing would be very oxymoronical... if thats even a word.
And maintaining free-trade, or taxless international trade has helped not only the USA, but the vast majority of countries all across the globes, all with varying GDP's.
I fully understand that you dont want your tax dollars, or even American tax dollars being spent in other countries, especially when your countrys poor could use the money. But its a very complicated situation, and even though we are told we have this transperancy, you dont really know the motivation behind giving away money.