One-to-many dimension values

My situation is the facts are import and export data, from the US to any other country. A trade (import or export) item is associated to one country (exports TO a foreign country, import FROM a foreign country). The fact naturally has a key to the Country dimension.

Countries are assigned to country groups. The groups are generally things like treaty organizations, or groups involved in free trade agreements. NAFTA, European Union, ASEAN (Southeast Asian Nations) are examples. A country can be a member of zero to many groups.

What is the best way to handle this in dimensional model? I've seen examples of 1 to Many fact to dimension examples, but this is really within the dimension. Outrigger? Bridge? Thank you!

A country -> country group bridge is the appropriate way to do this.

A problem you may have is if a country belongs to more than one group. It depends on how you plan to use it. For example, if both countries need to belong to the same trade group, it is probably less of an issue.