Trav'ling Canuck
Deity
- Joined
- Feb 7, 2018
- Messages
- 3,461
I don't think you're getting copies of the resources slotted in that city, rather the ones produced by that city's improved tiles. The only way those could be removed from the city is by swapping tiles to another city (if that's possible) or culture bombing them (if it's possible to steal them in that way).
That makes a lot more sense than my interpretation.

Then the main interaction for the trade route, after established, would be if all sources of that resource produced by that city were pillaged (assuming pillaging is still a thing).