Part of that is because Chicago is considered the baseline "accent" for many news broadcasters, radio personalities, etc. As a result, most Americans have heard that accent their entire life and therefore don't really interpret it as all that different.
I've found that it's the keywords that indicate where people are from within the Midwest:
Even that can differ between rural and urban. I've lived in the midwest for most of my life, and apparently there's all sorts of "terms midwesterners use" that I've only rarely heard anyone say, and most often only to point out that they don't say it.
This depends though. Did you live "all over the midwest" or in a specific state? The very same things people pointed they don't say, could be prevalent in a nearby state.