The US is 10% of TikTok's user base but 50% of revenue. Most of TikTok's most-followed users are American (https://en.wikipedia.org/wiki/List_of_most-followed_TikTok_a...). Canada, Australia, and New Zealand are probably another 5% of revenue. The UK may be not included because TikTok has stated that it wants to establish its global headquarters there.

There has been talk that Microsoft is interested in buying all of TikTok worldwide (TikTok isn't available in China; ByteDance has a separate, similar business there), which would be easier technically because TikTok's operations and algorithms would not need to be divided. India was TikTok's largest userbase until the recent ban; presumably a non Chinese-owned TikTok could quickly reopen there.