First if you us the convention center, you place the housing center off of where most of the housing actually is.

Convention centers are usually downtown. Mean population centers reflect the surrounding geography and can drift pretty far from an "idealized" circular urban area. My area's is out on an island for example, nowhere near downtown. Jackson county's is east of Raytown. I'm not sure why you'd specifically want to live within 20 minutes of the mean population center, so it wasn't the obvious interpretation of your original statement.

    Between $175k and $350k center on KCMO alone there are over 760 results.

No, there are 17 results once you filter for 2+ acres. Most of them are mislabeled or unimproved property. If you filter those out too (because this is a housing discussion), what remains within 20-30ish minutes are the two I linked.

I realize multiple acres of land is a bit of a silly requirement, but you're the one who suggested there are tons of houses with "several acres within 20 minute drive to a lot of US city downtown areas". That's why I was surprised.