The Bactrian camel's distribution looks like a plausible territory for a steppe empire.
Challenge: An empire matching the distribution map of a plant or animal
New Spain in a TL where the Mayans manage to hold off Spanish conquest, or end up being colonized by another power. The Spanish put a little more effort into colonizing Orejón as a result, but either the British or Russians beat them to Puget Sound.
Some sort of Carolingian-wank, maybe, possibly including a dynastic union with a Russian principality (more powerful, monarchical Novgorod, perhaps?).