US colleges are not the UN. The mission of US colleges is to educate American students. The int’l students are there primarily to provide global perspective for the benefit of American students, not to increase the future GDP of Tajikistan.
While it sounds great in theory to open the college classroom doors wide to poor , “deserving”, foreign students, the reality is that the ones with adequate english language skills tend to be the affluent ones. The few world leaders who were educated in the US as undergrads, were rich (King Hussein of Jordan; Bhutto family in Pakistan). For the most part, world leaders attended as graduate students, and there is already a generous funding framework for grad students.
http://en.m.wikipedia.org/wiki/List_of_heads_of_state_educated_in_the_United_States