The travel industry is voicing a common refrain: President Trump’s travel ban, terror attacks in Europe and a laptop ban represent a recipe for a potential sharp decline in visitors to and from the United States.

“When you hear words like ‘travel ban,’ it puts a big chill” on travel and tourism, James J. Murren, chairman and chief executive of MGM Resorts, said at an industry conference last week in New York.

Some data is backing up those concerns. Nearly 20 percent fewer people are visiting this summer from the Middle East, the focus of Mr. Trump’s travel ban, even though the policy has been blocked by American courts. As of early June, overall advance airline bookings to the United States were down 3.4 percent for this year’s summer travel season compared with the same time last year, according to ForwardKeys, a Spanish company that tracks air travel.

And NYC & Company, New York City’s tourism marketing agency, said in early June that it expected a 2.4 percent decline this year in international visitors to the city, the top tourist destination for people visiting the United States.