That makes as little sense as "men shouldn't have an opinion on abortion, because they're not female" or "whites shouldn't have an opinion on any issues affecting other races because they're not a minority" and so on. There is absolutely zero reason to dismiss a proper and educated opinion from someone on an issue just because it doesn't directly affect them or because of their nationality/race/gender/age...

And non-Americans can't have a proper or educated opinion on foreign matters or policies in different countries?