It’s researchers who are not at the top of their fields who will have a much harder time leaving America to find research positions, since academic positions and funding haven’t been easy to obtain in places like Canada, Europe, Australia, and Japan for at least two decades.
What will most likely be the case is that scientific careers will be halted temporarily or permanently from these funding cuts. Graduate admissions are harder than ever now, it’s harder to find a research position, and I can’t imagine how much more difficult tenure will be to obtain if professors can’t fundraise and publish. Industry isn’t always an option, either. A lot of researcher’s careers will face major setbacks, some unrecoverable, all due to the capriciousness of our rulers.