If you assume from the start that everybody is going to eventually buy Bitcoin, sure, you should buy it first. But if you're not stuck in this forever loop, you don't need to play, and you can ignore other nations buying Bitcoin. If you assume everybody in the world is going to speak Esperanto; you should probably learn Esperanto as soon as possible.
It does seem like a stupid circular argument that people will buy bitcoin because people will buy bitcoin, but is it? We buy bitcoin because it's a better money, presuming other people will recognize it as such. People aren't compelled to use better money, but why wouldn't they? And doesn't a money become better money as more people recognize it as such?