"The World Factbook provides information on the history, people, government, economy, geography, communications, transportation, military, and transnational issues for 267 world entities."
CIA World Factbook can provide background information and keywords that will help you continue your research to compare politics across countries.
Use the following language in a Google search site:.gov for any US-related government webpages, reports, press releases, statistics, et cetera.
Example Google Searches
This can help you identify US government agencies that may conduct and publish research in your area.