But earlier today, as I came down off a mountain, I was thinking about this. OK, so the simple explanation is interference from Spanish (vivo en Corte/Corti) But didn't we do this in high school? Didn't we do this lots in high school. When I thought about the placenames of me and my classmates -- Stirling, Denny, Banknock, Alloa etc -- yes, I thought of the sentence correctly: à Stirling, à Denny, etc.
Why were these ones correct in my head, but not Corte? If the Spanish interference was overwriting my French, why hadn't it made *
This would have to indicate a failure to generalise on my part -- that I had learned by rote, not by meaning. This was the first phrase I was ever taught with the word à in it, so there simply wasn't the support for me to understand the whole structure, so I memorised it as sounds, just as I do the words to songs in languages I don't speak.
But something else caught the back of my head. Maybe the reason I was confused was because of the exceptions, like... aha! Countries. There are no exceptions at the town level -- it's a stable rule. But in my school, we got towns and countries thrown at us at the same time, which made the stable rule seem unstable and arbitrary, leading to a failure to generalise.
Or, to put it another way, perhaps I generalised that the preposition was arbitrary...?