"I've heard about the alerts, but I'm not nervous," said Tom Rutter, who is traveling to Paris from Los Angeles. "I've been to many places where they had these things go on, and usually, they're very distant and the news makes them much bigger than they really are."
"I don't want to walk into trouble, but I'm still going. I'm not going to worry about being in Paris. It's a big city," Rutter added.
However, the U.S. State Department said this latest alert should not be taken lightly.
Traveler Tali Hiller has family in London and Germany and said she will be more aware of her surroundings.
"It's definitely a big concern because we know that they have been terrorist attacks in the past, so this is nothing to take lightly," she said.
Britain also issued a travel alert to its citizens on Sunday, and Japan and Sweden followed suit on Monday.
Experts said you don't necessarily need to cancel your trip to Europe because of the alert, but just to be more aware of your surroundings when traveling.
The alert comes after several intelligence reports of possible terror attacks in Europe. French authorities have reported nine bomb threats in the capital just in September, including three at the Eiffel Tower. Monday, French police arrested a man who is suspected of making several bomb threats in Paris.
Security forces in Europe and in the U.S. have been concerned for weeks of a possible terror attack linked to al-Qaeda. There are no specific targets, only that popular tourist areas and transportation centers in France, Britain and Germany could be among them.
The terror suspects reportedly include eight Germans and two British brothers, who may be of Pakistani or Afghan decent.
Pakistani officials said they believe five German militants were killed in an American missile strike close to the Afghan border. They also said those killed were believed to be German citizens in the region for terrorist training. Officials also believe that one of the Britons died in a recent CIA missle strike.
"They are a threat, not only to Germany but also to our allies and especially the U.S. because they are extremely anti-American," said German security expert Guido Steinberg.
Former U.S. Homeland Security Secretary Michael Chertoff urged Americans in Europe to take precautions such as knowing where they are in a city and identifying an exit at major tourist sites. He also explained why the alert is so broad.
"What the authorities are wrestling with is they do have some information that there is a threat out there and they feel an obligation to share that. At the same time, you don't want to alarm people, particularly in the absence of specifics," said Chertoff.
Intelligence and law enforcement officials claim they have information that terror teams could launch commando-style attacks similar to the 2008 attack in Mumbai, where 175 people were killed after an organized band of extremists went on a shooting spree for three days, targeting high-profile places visited by westerners.
The U.S. State Department said any Americans traveling in Europe should notify their American embassy of their whereabouts, and if they do see anything suspicious, they should contact authorities.
The Associated Press contributed to this report.