If you're worldbuildering those enemy cities' culture, you're probably getting very wrong results. Take a tile next to a 40% (with 200 culture, say) city. That tile has 100 culture on it guaranteed - but it also has another +20 culture for every turn that the city has at 10+ culture (and still producing at least 1 per turn). And make that +40/turn once the city passes 100 culture. If you set the culture in WB, you probably only gave that tile 100 culture or a bit more.
I don't know of a good way to to do an accurate sim, sorry. But in real life culture bombs are pretty much useless for claiming tiles when used in someone's core, unfortunately.
I don't know of a good way to to do an accurate sim, sorry. But in real life culture bombs are pretty much useless for claiming tiles when used in someone's core, unfortunately.