If the TARDIS does land in Prohibition America I suspect it'll all be jolly speakeasy-keepers and aliens conducting shootouts in fedoras and black jazzmen who everyone treats with the greatest of respect. They wouldn't want to mess with those American sales.

I wasn't that surprised by the random black aristocrat - there were some rich mixed-race Creoles kicking around France at that time, though they'd probably have got muttered at at Versailles for being parvenus rather than for being black - but the general dumbing-down of that episode did annoy me. They missed a lovely chance to show how the eighteenth century could be much more alien than the fifty-first. Especially since everyone in the future seems to shop at H&M.