I didn't mean that about all midwestern accents, just some.
Whenever I run into someone from another state or another part of the country, I can't say there's typically any sort of notable accent. I think there is more neutrality in the American English accent than is recognized at times.
I recently spotted something that sounded very New York in the speaking of a couple
ESL students. I asked them if their friends or coworkers are from N.Y. Sure enough, that was the case. So, there are accents sometimes. Accents from the N.Y. area tend to stand out. It was kind of interesting to hear how it was rubbing off on a couple people whose second language is English. It was how they pronounced short "o" type sounds that gave it away.
dog, talk, bought, etc...