I have to agree with you that American media is unnecessarily suspicious of non-American swimmers (and athletes in general) doing well. There's even rumblings on other sites about how suspicious the sudden rise of Canadian women is. I find this interesting considering the US's history with performance enhancements, both caught and obvious yet allowed. As a Canadian it was frustrating to watch Ben Johnson embarrass our nation while Carl Lewis had to remove syringes from his neck to get the gold (metaphorically, of course).
However, Sun is a proven cheat and has a terrible attitude. I only heard praise of Hosszu in 2016, the Canadian media was fawning over her. I think Sun is a strange hill to die on to defend non-Western athletes. Efinova has done much more to recover her image and has earned the, marginal, respect of her competitors again.