Ruling on traveling to disbeliever countries for study

A course was offered to me, O Shaykh, in my field of work in America. Is it obligatory for a person to go there for this study for the sake of benefit in his field of work?
By Allah! I do not know. If the man who was selected by lottery to go to America or other lands of disbelief is a caller to Allah who has knowledge, has the ability to persuade, and has determination to call to Allah, then his going is good without doubt. This is because disbeliever countries are currently in a strait; they want someone to relieve them from their situation regarding religion, and some of them even regarding worldly matters, economically and practically. So this is good.As for a person from the general public, I do not see that he should go: [Al-Talaq: 2-3]; because what has reached us is that many of those who go there return without good character or religion—seeking refuge in Allah—not all of them, but many of them. And among them, praise be to Allah, are those who are good, fertile ground, good plants, benefiting people and benefiting themselves.