Bulgaria
Tourist Visa Required? NO
Requirements

U.S. Passport holders do not require a visa for stays of up to 30 days. A valid U.S. passport is required along with proof of onward transportation.

 
Business Visa Required? No
Requirements:

U.S. Passport holders do not require a visa for stays of up to 30 days. A valid U.S. passport is required along with proof of onward transportation.

Requirements are based on Embassy/Consulate in : Washington D.C.