I'm running a pretty large modpack and as cool as the cities are they are way too laggy. I didn't realize that loading a world with the mod would cause the world to now be dependent on that mod even though there is nothing there that requires the mod generated in the world. is there anything I can do in the game files to get the world to work without the mod?

That's hard. You could make a new world and copy over the world file to that new world. I think that might work