You are right: at this moment US universities are still regarded as better. But I hope you recognize that this situation must change if the top minds in the US economic and education system are emigrating. They are not only taking their business knowledge with them, but also the capability to build up their local education system. The result of that won't show overnight, but it will happen.
Are 100% of the top minds leaving? No, not even close. Some are choosing to go overseas. While it will hurt, it won't be nation crippling like the #### like Samson think. There are plenty of bright people sticking around and working here.
For all the geniuses that appear to be going back to China, I find it amazing that their ability to innovate or invent anything worthwhile is pretty much 0. Take a look at how most of what they make a cheaper, shittier copy of a European/American product. For example, look at the blatant BMW ripoffs being produced over there for a good example of what China isn't capable of doing.
And let's be honest. The top of the heap are sticking around and working for companies like Google.