Some ai assisted takes here

https://www.quora.com/Did-T-S-Eliot-retain-his-American-acce...

He's from a Boston Brahmin family so I doubt he had a real missouri accent to begin with

Edit

These are apparently from 1930s https://writing.upenn.edu/pennsound/x/Eliot.php

Where some Midwestern features are still present ?

Especially here, after the 2m32s mark

https://media.sas.upenn.edu/pennsound/authors/Eliot/Eliot-TS...