You can sign up from anywhere, in principle (CI and Alcor list a number of non-US members). The major issue is that it will obviously cost more to transport you to suspension facilities in the US, while avoiding damage to your brain cells in transit.

I'd guess that getting your local hospitals and government to allow your body to be treated correctly would be the biggest non-financial problem.

I live in Israel, and even if I had unlimited money and could sign up, I'm not at all sure I could solve this problem except by leaving the country.