Another point to consider here is that VPNs usually have a pretty low monthly data limit and kids won't bother paying for a VPN to access something they can also access through Instagram Reels or YouTube Shorts.
A third thing to consider is the network effect. If (hypothetically) in Russia, every other teen uses VPN to post on an otherwise unavailable platform, there's enough content made by Russians there to get fellow Russians interested. OTOH, if in the US, the majority of the kids stop going there, there will be less relatable content that kids would be interested in. Those that exited the platform would publish their stuff elsewhere, and that's where everyone would eventually end up going.
A third thing to consider is the network effect. If (hypothetically) in Russia, every other teen uses VPN to post on an otherwise unavailable platform, there's enough content made by Russians there to get fellow Russians interested. OTOH, if in the US, the majority of the kids stop going there, there will be less relatable content that kids would be interested in. Those that exited the platform would publish their stuff elsewhere, and that's where everyone would eventually end up going.