Apologies in advance, I'm rushing to write this and get back to work. My dissertation is on regional variation in African American English, and I'm one of a handful of linguists looking at regional variation in AAE. I haven't yet written about my findings for the general public on my blog (coming soon!) , but the short answer is that, yes, there are noticeable differences in AAE accents by region, and those regions pattern with the Great Migration.

Chicago is more likely to sound like Mississippi than Texas, but you're basically correct. The broadest patterns are a strong band up the Mississippi river connecting the Gulf States to the Great Lakes, a southeast cluster with Florida and Georgia sounding similar (sharing, for instance, a greater likelihood of having the COT-CAUGHT merger), and the Northeast patterning broadly together, but with distinctions, so DC and Baltimore (the DMV) patterns together and different from Philly, New Jersey, and New York.

North Carolina also has its own thing going on (The African American Vowel Shift in the AAE sociolinguistics literature was first described there), patterning broadly with that Mississippi river accent, for historical reasons.

The standout features (that is, not a full description of each region) are:

Mississippi River (Gulf to Great Lakes) and parts of North Carolina: (1) reversal of the nuclei of ey (as in FACE) and e (as in DRESS), (2) reversal of the nuclei of iy (as in FLEECE) and i (as in KIT), (3) raising and fronting of æ (as in TRAP) so the vowel in trap sounds like other folks' vowel face, (4) raising of wedge (the vowel in STRUT). So, for instance, the vowel in strut sounds like other regions' vowel in book.

Florida and Georgia: COT-CAUGHT merger (where the vowels in the words cot and caught sound the same), and sometimes raising and backing of æ (TRAP), so the vowel in trap sounds like the vowel in other regions' pronunciation of bed.

Washington DC and Baltimore, and nearby areas (the "DMV") show fronting of the vowels in GOOSE and GOAT (as does the entire West Coast), but maintain a strong distinction between the low back vowels in cot and caught, and generally don't show the reversals in that Mississippi Great Migration region.

Further up the east coast the accent is almost aggressively the opposite of that Mississippi river pattern.

So while white folks from Buffalo or Rochester sound fairly similar to white folks from Chicago or Minneapolis (because of the Northern Cities Vowel Shift), Black folks from New York sound noticeably different from Black folks in Chicago or Minneapolis (who sound more like Mississippi). If you think about the regional patterns already described for white Englishes -- Northern Cities Shift, midlands accent, Southern accents -- Black accent patterns are basically rotated 90 degrees and change more from East to West than from North to South. A white person from Houston will sound more like a white person from Atlanta, all things being equal, than a Black person from Houston and a Black person from Atlanta (assuming Southern American English and African American English and no sampling shenanigans).

I promise I will return with links to more detailed explanations, but in the mean time:

My 2015 paper on regional variation: Jones, Taylor. "Toward a description of African American vernacular english dialect regions using “Black Twitter”." American Speech 90.4 (2015): 403-440.

My dissertation: Jones, Taylor. Variation in African American English: The Great Migration and Regional Variation. University of Pennsylvania (2020).

And some other good work on regional variation:

Kohn, Mary, and Charlie Farrington. "A tale of two cities: Community density and African American English vowels." University of Pennsylvania Working Papers in Linguistics 19.2 (2013): 12.

Wolfram, Walt, and Erik Thomas. The Development of African American English. John Wiley & Sons, 2008.

The American Speech special issue on the Corpus of Regional African American Language (CORAAL)

The Corpus of Regional African American Language (free and open to the public)

Farrington, Charlie. Language Variation and the Great Migration: Regionality and African American. Language. University of Oregon (2019)