Everyone is suspect. It is easy to make arguments as to why Country X is particularly suspicious but note that the most suspicious country has changed many times in the past 30 years. And the one constant reality is that athletes--no matter where they are from, how much money they have, how talented they are--cheat. Half of the major league in the 1990s cheated. The entire peloton in the Tour De France cheated. Probably Lasse, Mary Slaney, Dieter Baumann, Ma's Army, Regina Jacobs, numerous Kenyan runners recently, probably all sorts of 50 year old triathletes and runners, all the folks who cut courses. . . .
What is sad is that probably a lot of the good 1500 runners are clean. Jim Ryun ran 3:33/3:51 on a dirt track in obsolete spikes. Probably clean (or at least he was not on EPO because it just wasn't available). Super spikes and nice track and he is under 3:30 and that was over 50 years ago! I have no doubt that there are people who can run 3:28 or faster clean but there are more people who can run 3:32 clean and will take drugs to get to 3:28 or faster.