[thaumasiotes]

> If I were American I'd:

> a) start saying "t" in the middle of a word as a "t" instead of a "d"

Americans do not have a distinction between intervocalic /t/ and intervocalic /d/. (Though you have to be careful - that analysis requires you to commit to a "syllabic /n/" model of words like "kitten".)

But while /t/ and /d/ are pronounced identically in that context, you can't say that /t/ is being pronounced "as /d/". They are both flapped, which is a sound just as distinct from [d] as it is from [t].

[brigandish]

Budder.