WASHINGTON, Sept 28 (Reuters) - The United States has included Croatia in its visa waiver program, allowing its citizens to come to America without a visa for a stay of up to 90 days, Homeland Security Secretary Alejandro Mayorkas said on Tuesday. "Today’s designation of Croatia as a new participant in the Visa Waiver Program is an important recognition of our countries’ shared economic and security interests, Mayorkas said in a statement.