The question of when and where is Ansteorra and how we got here is very open. 
I for example view Ansteorra as a separate European country and at the same time think of it as England. I think old Atenvelt is France and old Merides as Scotland. I skip around in time and rewrite my adventures in the SCA to fit my persona story. To me the year is 1206. Of course Ansteorra has some new fangel customs --like rapier fighting which isn't done other places. It also has some old fashion people like Norsemen. I used the "magic eraser" to eraser strange clothing and make it into my period. You know about the "magic eraser" that is the thing that gets rid of cars and basketball hoop and other such stuff and makes everything period in our memories. My husband acquired land in Ansteorra and like every feudal noble that I know we just spread our interest to here also. When things are troublesome in France, like it is now I find Ansteorra a haven. I would suggest you don't worry about how you got here. It is like Avalon it just shows up and you were here. 
Willow de Wisp