The U.S. State Department issued a "worldwide travel alert" late on Monday due to increased terrorist threats, in the latest security red flag for global tourism.
It warned of the likelihood of terror attacks continuing as members of the so-called Islamic State (ISIS) returned from Syria and Iraq. It noted that attacks had taken place across the world over the past year, including in France, Nigeria, Denmark, Turkey and Mali.
The "alert" holds until February 2016 and follows the terrorist attacks in Paris on November 13 that killed 130 people.
The State Department warned that people should be particularly cautious at festivals and events, as Americans prepare for the holiday season, with Thanksgiving this Thursday.
It issued a lower level "worldwide caution" in both January and July.
"Coming right at the beginning of the holiday season, and on the back of ongoing states of emergency in France and Belgium, (this warning) is surely a hit to confidence," Ian Bremmer, founder of political risk firm, Eurasia Group, told CNBC on Tuesday.
He added that with presidential elections looming in 2016, security concerns could impact candidates' gamesmanship and the country's future policy.
"The bigger long term issue is the impact on elections, where security and foreign policy issues are crowding the top of the agenda. Candidates on both sides of the spectrum will have to show their toughness if they want to succeed in that environment, (it) can absolutely impact the eventual policy trajectory of the country."