Many are skeptical of Ethiopians/Kenyans training in those countries because they are more corrupt, have easier access to drugs, have less testing infrastructure, and have more financial incentive to dope. If someone is raised in USA (but is Ethiopian in ancestry), especially a high schooler, I wouldn't suspect them to be doping. Doping is a problem here too, but its trickier because the drugs are harder to obtain and there is less culture around it. Its less about corruption and more about greyarea doping (see NOP) and skirting positive thresholds by microdosing (not unique to US).
Not sure if you've seen the state meets in India where the bathrooms are loaded with EPO syringes and steroid packaging, and 75% of the fields dropped after learning there would be drug tests after. Its a bigger problem than you think. That 4x4 team from India at worlds is looking a bit sketch now.
Kenya has cracked down on drug testing the past few years and we've seen some names popped that you would think were untouchable/too big to fall. I don't get the feeling Ethiopia has had the same crackdown as Kenya.
My gut tells me Shericka Jackson, Shacarri Richardson, Faith Kipyegon, Tsegay, and Assefa are doping of the world class women. Feels easier to speculate on women since, imo, PEDs have a more noticeable physical impact on their body, and a bigger performance boost from not doping. Kipyegon and Shacarri look noticeably more toned in an unnatural way at worlds this year than they looked last year. Shacarri reminds me of what I thought about Coleman before he got banned (I speculated he was doping then), unnaturally toned. Coleman looks noticeably more normal now, probably learned his lesson. Tsegay and Assefa I am less familiar with, but their performances also raise flags.
And lastly, many Americans work very hard. I know tons of Americans running over 110 miles per week in college. Genetics, growing up at altitude, etc. make a difference.