While there would be no immediate consequences for World Heritage sites, the withdrawal by the United States may affect Unesco in other ways. According to Dr. Stefan Simon, the director of Global Cultural Heritage Initiatives at Yale University, “With the U.S. once responsible for approximately 22 percent of Unesco’s budget, of course the announced withdrawal is detrimental, and would painfully reduce Unesco’s ability to fulfill its important missions, such as advancing and promoting literacy, gender equality, freedom of expression and scientific collaboration.”

If the United States withdraws from Unesco, it would remain a state party, having signed and ratified the World Heritage Convention. “There is one consequence only,” Mr. Papagiannis said about the United States withdrawal. “The U.S. cannot be elected to the World Heritage Committee,” a managing committee made up of elected representatives from 21 countries. The committee is in charge of allocating financial assistance and determining what sites are included on, or removed from, the World Heritage List.

Despite no longer being a paying member, the United States would be able to continue to submit sites for World Heritage List consideration. The World Heritage Committee will next meet in Bahrain from June 24 to July 4, 2018. “The leadership of the U.S. is crucial in this debate,” said Dr. Simon. “Its voice will be thoroughly missed at the table.”

The United States played an integral role in the creation of the World Heritage program. Russell Train, the former administrator of the Environmental Protection Agency who is often described as one of the primary architects of World Heritage, talked about the importance of the concept in a 2002 speech at the 30th Anniversary of the World Heritage Convention in Venice, Italy. “The World Heritage Convention itself represents a partnership among 175 nations,” he said in his speech. “I see the program as an opportunity to convey the idea of a common heritage among nations and peoples everywhere. I see it as a compelling idea that can help unite people rather than divide them.”

There are several benefits for sites that are included on the World Heritage List. Unesco provides leadership on maintaining the health of the sites, including a focus on sustainable tourism. “An important component of what we do is providing guidance for managing tourism numbers in a sustainable way,” Mr. Papagiannis said.