Okay brilliant. Lots of businesses and industries employ foreign workers for various roles. Immigrants coming to a country and offering their skills is brilliant and something that we do a lot in the UK (pre-Brexit). This does not make the people who come over British.
It seems most of you cannot distinguish between immigrants who move to a country and work there and contribute in whatever means, and what someone's actual nationality is. Mo Farah lives and probably pays a considerable amount of tax in America - he is still British.
Do you really think these Kenyans would still be 'putting their lives on the line' for your country if it didn't mean becoming an American citizen and a cushty life as a full time runner? No of course they wouldn't, they're doing it for the sole reason of an easy (easier) route to major champs.
Again, all for people emigrating away from tough environments for a better way of life (I've been to Kenya, so I know exactly how hard their lives are), but they're still Kenyan nationals who should only be able to compete for their country. No different really from those who're paid to run for Turkey, Bahrain etc.