From the Document: "Bulgaria is a southeastern European country located along the Black Sea. After decades of single-party communist rule and a turbulent transition period during the 1990s, Bulgaria joined NATO in 2004 and the European Union (EU) in 2007. The United States cooperates with Bulgaria on a range of security issues. At the same time, U.S. officials have urged Bulgaria to strengthen the rule of law."
CRS In Focus, IF11725
Congressional Research Service: https://crsreports.congress.gov/