CJ is not restricted to affiliates from the US or any particular country. CJ is a platform which links merchants with affiliates. Some merchants may not approve affiliates from certain countries. As for tiers, it's again up to the merchant to decide if they want to have multi-tier payment terms.
No, I mean another thing. I read in the cj chapter of rosalind gardner's affiliate handbook: Multi-Tier: Yes, with restrictions. They allow only U.S. and U.K. publishers to earn commissions from introducing new publishers to their service. What's up with THAT? I've contacted them regarding this seeming discriminatory practice, however I've received no acceptable (IMHO) explanation for the policy.