PVD (well, all of Rhode Island, not including Fall River/ New Bedford): 30,224
https://mtgis-server.geo.census.gov/...Default&f=html
All of Tennessee has 2309 people in census tracts above 20k, from one census tract in Knoxville (so Memphis and Nashville have none).
Indiana has 8,044 people in census tracts above 20k in one tract in Lafayette.
Michigan has 3 counties with census tracts above 20k, with populations:
Wayne: 4,656
Washtenaw (Ann Arbor): 6,052
Ingham (East Lansing, presumably): 11896
North Carolina has one tract with 2000 people in Mecklenburg County (Charlotte)
Outside of Dallas/Houston/Austin, Lubbock has 6,374 people (presumably Texas Tech housing, but I didn't check).
Surprisingly to me, Las Vegas has 26,144 people and Reno has 2,049.
Phoenix has 20,351 (13,807 in Maricopa, 6,544 in Pinal) and Tucson has 5,138.
Iowa City has 4,165 and Ames has 4,837, both presumably student housing.
Cleveland has 3,431 and Cincinnati 3,836.
Idaho has 7,781 in Madison County (Rexburg, perhaps? I think there's a BYU branch there).
Utah has 13,203 in Utah County (probably also BYU)
Alabama, Kentucky, Kansas, Oklahoma, Nebraska, West Virginia, Alaska, Montana have zero.