It's more that a lot of the foreign athletes are a product of the American athletic system. Lots of the athletes competing from other countries have lived here as teens and went through American HS and college athletic programs. Their excellence is due to the American competitive system and associated resources. But then when they win a medal for "Lantitola, a small island nation of 10,000 people", it makes it seem like that country was able to produce a top athlete. But in reality, the athlete's family moved to the US years ago because their kid showed promise and they wanted him to train in the best programs possible.