I've been trying to come up with recs on and off all day, but all I can think of are AUs where the anachronisms set my teeth on edge. Your historical AUs are pretty much the only ones I can think of off the top of my head where the setting is more than a nifty backdrop.

I do have this: The Bubble Chamber, by Duncan Johnson. It's set during the Red Scare, but with the aid of time travel rather than an alternate universe--it's a Doctor Who fic--and it stood out for me because it incorporates the political atmosphere of the time (which is necessary to the plot) without co-opting it.