Other countries subsidizing education and the more developed ones reaping the results is very much a zero-sum game. Immigrant myself, I'm all for people getting better lives, however if you're talking churning 10-20% of a small country's doctors or nurses to the US it would be catastrophic.
There's more nuance, in that it's not just a one-way transfer, and education is not just subsidized by the country.
On the former, Phillipines are sailant example of sending people abroad to get goods and money back, but this happens at some scale for all other countries with a significant emigration. The money fed back in the original country is usually not something to sneeze at.
The other part is, education benefits everyone beyond the single individuals. Having a strong enough education programs that opens the door to move to other countries with strong requirements is an asset that also benefits the origin country. In most countries only a small portion will go abroad, so improving the overall level of students stays important, and the bigger the pool the more you have inter-student emulation + economy of scale effect.
Also the monney spent by the country into education is not just for single children and has a global societal effect.
All in all, IMHO it's not a black and white as "that kid wasted our tax dollars by going abroad"
