Rome wasn't built in a single day. Trends start way before the final line is crossed. You can address them early or let it be and hope it goes away by itself.

If you waited until the day when Americans have to go to China for an education, then the US is longer in a position to deal with the problem as effectively as when it just started losing foreign-born scientists.

The US was built by immigrants. That is the root of its power, a gathering place for talents all over the world. If you still question whether it is of any concern for immigrants, especially high-skilled ones, to feel unwelcomed here, then I afraid I have no arguments that can sway you.