For one, geopolitics and international economics isn't a zero-sum game. There are things that are good for everyone. A rapidly developing trade partner helps us, too. For another, when we educate a large number of their big players, we have basically imparting our values on the most influential people in that society. In addition, those guys, being educated in English and having made contacts with many in the U.S., will naturally be more inclined to do business or collaborative research with Americans in the future. Even when a Chinese company does business with an Indian company, they will be collaborating in English. That's a natural edge for our citizens, especially their fellow students in grad school. As a small example, my time spent with Indian, Eastern European, Chinese, and Korean TAs in undergrad really enhanced my ability to understand their accents.
So, I think it's pretty obvious that there is an ideal number of students educated here who immediately return to their home countries. Whether that ideal is higher or lower than the actual number today, I don't pretend to know - but I think we'll be fine as long as we have world-class universities located on our soil. If we really want more of them to stay, we need to be able to streamline the visa/greencard process for educated people. We also may want to make financial incentives (e.g. loans that are forgivable upon attaining permanent residency/citizenship) to keep them around. Either way, this "problem" is not much of a problem at all, and even so has easy fixes.