It could of course also be that the five fold increase is because China itself is becoming more competitive. I'd be a lot more worried if there was a five fold increase of American scientists leaving for China and sending their children there to study. But that does not seem to be happening. American universities are still quite prestigious, also inside China. Depending on the field Chinese universities can be quite prestigious as well, but given the choice of studying in the United States or China many people from other countries would given equal opportunity still choose the United States.

It is true that US immigration is horrible, but that goes for may other countries as well. I don't know what the cause is or whether it is something that you should even want to repair.