The flip side is that foreigners who invest in America aren't taxed at all. At least in Singapore, I know people who invest in the US stock markets and pay not

The flip side is that foreigners who invest in America aren't taxed at all. At least in Singapore, I know people who invest in the US stock markets and pay not a single cent in capital gains taxes or dividend taxes (Singapore does not tax these). I'm not sure the citizenship based taxation makes the most sense.