The Blacks are new, relatively speaking. Starting around the time of the Conquista if Dracula was the first.
The White Court, which uses Etruscan as its official language, quite probably was the original "European" vampire. Maybe they were originally behind Roman patricians? Their move to eliminate the Black Court makes more sense if the Black Court was encroaching on their territory.
Their moving to North America is their expanding operations.
In fact, I have this complicated and longwinded theory that to understand the first half-dozen Dresden books, you have to view Chicago as a kind of supernatural Casablanca that both the Red Court and White Court were making power plays to take over; and Harry wandered in before Marcone "stole" it as a Freehold. Too valuable of a nexus.