There’s no way they could generate similar revenue per user. Revenue per user depends on much advertisers are willing to pay and there are a couple of differences:
1) Targeting: Instagram has exceptional ad targeting because it utilizes facebook’s existing data which TikTok tool doesn’t have.
2) Online spending: In theory wealthier countries / demographics should have higher online spending. May also have correlations with gender, age, employment status, number of digital devices, delivery infrastructure, etc.
3) Advertiser relationships: the real customers have to want to put their stuff next to your content.
4) Political risk: if many countries ban it, it’ll lose access to a lot of high value markets.
Lastly, profitability doesn’t always come later particularly for high bandwidth applications. Personally I’ve been getting a higher number of ads from YouTube but they are exceptionally poorly targeted (I skip at-least 90%). I would expect google to have as much data as anyone. The only explanation I have is that it’s simply too expensive to produce video ads to have an efficient targeted ad market.