Country hashtags are systematically defined for each country in their Actor Atlas #tag guideline. Each hashtag is constructed by adding a country's Alpha 2 ISO code to a topic hashtag:

There are country hashtag pivots on dedicated wikis for

For most countries, there is a #tag guideline in the Actor Atlas:

Select a continent's tab for a link to a country's #tagcoding guideline and for its Alpha 2 ISO code.