The argument here can be boiled down to whether or not you believe that Kenyan born runners are genetically superior to American born runners.
If the answer is no, then the playing field is level. If an American kid wants to skip class and focus only on running, they can go right ahead (I know a number of runners who have done this, usually to their detriment). If they want to hold off before going to college, take a few years and run after high school, go back as a 20 year old Freshman, I am not aware of any rules preventing them from doing this. Age shouldn't have anything to do with it though, because look at World Juniors and tell me that our best college seniors can compete for Gold Medals against 19 year olds. It is certainly a factor, but in no other stage in our sport is there age grading so why get used to it in this venue? I also believe that there is nothing more "American" than working hard to have a better life for yourself. This, incidentally, is where I think the difference between American and Kenyan runners lies at this level. Motivation for an American to run fast and take home his plaque and do his best is great. Motivation for a Kenyan to have a better life for himself and possibly his family is greater. I concede your point that they are taking scholarships from American runners. Hopefully everyone just writes it off as charity and feels good about themselves for helping.
If the answer is yes, and Kenyan runners are just BETTER, then All-American status should be reserved for Americans in the NCAA Championships. .....They already do that? Oh. Well then having foreign runners in the race can only make our runners faster.