I agree that the US has been taken advantage of by the world. I was watching this interview, and this guy said something to the effect of : after ww2, the US felt it had the responsibility to help nurture the world back to peace and democracy. To help shape the world into a peaceful one, and to avoid authoritarianism. Hence, it's foreign policy was geared to support this. Support with money, tech transfer, human capital/knowledge.
Trump is right to want to rein this in, it has cost the US too much. But he could've chosen more diplomatic ways to do this. I am sure foreign leaders would be more receptive to such an approach.