Actually Messi, Oxford and Cambridge Crew teams are loaded with American and foreign athletes; but you still have not answered the fundamental question of competition.
Are you saying that Americans can not compete with the rest of the world?
American kids have not been denied scholarships. The universities did not award them scholarships because they did attain the "required" competitive standard. As an American college-educated track and field/XC athlete you should know that the NCAA Division I competition is as competitive in some events as the Olympics if not more so.
The Olympic "A" Standard for the 100m and 200m is 10.16 sec. and 20.50 respectively. The current NCAA Champion (A Canadian) ran well below this mark, but so did the ENTIRE field (several Americans) in the 100m and 200m finals, either in the final or during the season. The best of the best NCAA Division I athletes are world-class - this is a fact. The emphasis is on world-class, not American class, not 5A or 4A, but world-class. American high school athletes, their families, friends, and everyone regardless of where you are from should understand that the athletes competing in the NCAA are the very best. To go in thinking that this is some high-school dual meet is not realistic and is an insult to the sport.
Coaches jobs are tied to performance to some degree. Are you saying that you would not recruit a Czech javelin thrower, or a Jamaican sprinter, or German Heptathlete?! Of course you would. The flip side of this on the College Coaching Job thread are coaches and assistant coaches being belittled everyday, mercilessly, because they can not win or put a winning team together. A winning team means putting the "best" team you can assemble. Let me put it to you this way. If you or a loved one needs an incredibly difficult operation; are you going to say, "I only want people from Iowa to work on me" or are you going to ask, "who is the best and will they perform the operation"?
Another issue you failed to take into consideration is that these foreign athletes are completing degrees in their second or third languages. They are hundreds if not thousands of miles away from home in a new and sometimes very different culture and they are still producing the goods. They make the entire college experience better. At the very least, if you were a good teammate, you would have a place to say in Africa, Europe, Asia, etc.
Between the great middle and high school coaches throughout the US, personal trainers, sports camps, sports academies, travel teams and Crossfit. Are you saying that with all these amazing resources available to American high school athletes they are are at a disadvantage to Kenyans, Latvians, etc.
Not to belabour the point but train, compete.
The plan is simple;
Sleep
Study
Run
Lift
Stretch
Rest
Repeat
After 4, 6, and 8 years you will be competitive.