Well, assuming that the asteroid strikes are analogous to SM Stirling's Peshawar Lancers, I'd imagine that the Napoleonic Wars are going to grind to a halt pretty darn quick.
I could see Spain and Portugual doing fairly well after the former emulates the latter and moves it's government to the New World along with most of it's population. I could also see Britain doing fairly well as well, though not as well as in Sterling's novel. Whatever population they could get out would probably head to either S. Africa or Australia.
Russia would definitely be different tho I don't quite know how.
The real wildcard would be France under Napoleon, I could easily see France Outre-Mer establishing itself much earlier and with much more vigor than in Sterling's work. Perhaps stretching as far as Egypt...