To underscore Obama's message, his Homeland Security Secretary Jeh Johnson held a photo op at Washington's Union Station just before boarding an Amtrak train to Newark, N.J., on the heavily traveled Northeast corridor, en route home for the holiday
"It should be obvious to the public that there is a heightened presence" of law enforcement officers at train stations, airports and other public places, Johnson said. "We are working overtime to protect the homeland."
Some travel analysts expected airport delays as a result of heightened security.
But at Chicago's O'Hare International Airport, one of the country's busiest, Kirsten Bohling, 27, said she was pleasantly surprised by how painless her check-in went.
"Lines are way shorter than I thought they would be and moving 10 times faster than I thought," she said. "I think they were really really prepared."
The FBI sent a bulletin earlier this week to police departments across the country warning of possible copycat incidents after the Nov. 13 Paris attacks and sharing intelligence on how the attacks were carried out.
The U.S. State Department also issued a worldwide travel alert on Monday warning American travelers to remain vigilant, particularly when visiting foreign countries.
As many as 3.5 million people were expected to line the 2.5-mile (4 km) route of the Macy's parade in New York, according to organizers. City officials have made numerous public appearances in recent days seeking to reassure New Yorkers and tourists.