I haven't begun following it yet, but I've read on io9 and other blogs about
Fringe and how that show has alternate world(s) very similar to OTL except with
several major differences, including obligatory airships. I've had similar ideas myself, with
specific quirks in otherwise unchanged timelines. So let's call this concept a "Fringeworld"- a place very similar to OTL, except for certain mysterious changes. And with the lack of butterflies a la Stirling/Turtledove, of course, causing the world to look very similar to our 2011, even if the HRE is still in existence or something like that. Actually, a better example would be
Watchmen in terms of overall look and feel.
Here's a snippet from my Fringeworld, which I'm not done yet. I'm using "ohistorical" as shorthand to mean "historical in our timeline."
U.S. territorial changes
Nova Scotia joined the ohistorical Thirteen Colonies in rebellion, becoming the 'first brothers' alongside the Vermont Republic, the first two states to follow the original 13.
East Tennessee seceded during the Civil War and subsequently became a state, similar to West Virginia.
Baja California was annexed in the Treaty of Chapultepec at the conclusion of the Mexican-American War, along with the other ohistorical states.
U.S. governmental changes
The OSS remains in existence, even though the CIA was founded separately.
The Department of War was not renamed into the Department of Defense.
I've actually got more states in mind, but not much. Anyways, what's your
Fringeworld?