[quote=@Kingfisher]
Oh and, as to how the empire could have come about; perhaps there was a giant concentration camp hidden away in Canada? Towards the build up to the war, Vault Tech and the US government were not only locking away communists, but also people of Chinese descent. 

When the bombs fell, the camp could've fallen into a state of disrepair and the inmates, now very much anti capitalism, could have repurposed the facility as a sort of base. Fast forwards two centuries, and you have the Tinsui.
[/quote]

Oh man! An internment camp Vault? That sounds EXACTLY like one of Vault-Tec's ideas. "What if communism really IS the answer?"

So the Tinsui built their Empire on the foundation of their vault, and then surviving Chinese sub crews and soldiers in and around Alaska have made their way to Vancouver. Because of the squabbling in Mojave and Southern California, no one really noticed until now, when the Empire has shown nuclear capabilities.