City as in City-State...as when Florence and Venice and Rome were each powers unto themselves, ruling the city proper and the lands surrounding them, with wars, skirmishes and trading between them.
I don't think Latin has a word for what the states in America are, so the course uses urbs for city and civitas for state
It's kind of the city and the region around it that is under the control of the city. This languagw is from a time and place where city-states were the norm, so they mean something different than we do when we say state.
"Bostonia" almost sounds like "Bastonia" or even "Pastonia" here. Again, latinizing place names should also result in the pronunciation being Latin (as reconstructible as possible, of course)