It's a production level achievement; when you have at least 200 production in one city, it pops. Terrain and population matter for this achievement, so find a location for your city with lots of production terrain (mountains, hills, production bonus resources, and trees) within it's cross and pump settlers into it (maximum population is 31). Build production increasing buildings (workshop, iron mine, and factory) and research production increasing techs (engineering, railroad, nuclear power and electronics). Set your government to communism (2x production), and play as the Americans (3x production).