NEW YORK  — From cafes in New York to tailgate parties in the heartland, the bloodbath in Paris is forcing Americans to ponder the awful possibility of terrorist attacks on “soft targets” in the U.S. such as restaurants, bars and other ordinary gathering spots.

“Maybe I’m more jittery,” said Jordan Veneman, sitting at La Colombe cafe in Manhattan’s SoHo neighborhood. He said that when a car backfired shortly after the attacks in France, he immediately thought of a bomb.

Counterterrorism experts say well-coordinated assaults carried out by foreigners are less likely in the U.S., in part because of tougher accessibility to the mainland and better intelligence-gathering since 9/11. But they acknowledge such attacks cannot be ruled out.

They worry even more about the possibility of “lone wolf” attackers who may have no direct connection to extremist groups such as Islamic State but embrace their ideology.

“It’s impossible to protect everything and everyone all the time,” said Lauren C. Anderson, a retired FBI official who served in Paris and headed the international terrorism program for a New York task force.

She said intelligence-gathering and sharing is crucial, but added that everyone has a role: “The front line when we’re talking about this now is people being aware of what’s going on around them.”

In the crowded lobby of the Ace Hotel in Manhattan’s Garment District, Daniel Bellino, who works in the restaurant industry, said authorities in New York, where memories are seared with images of 9/11, have done “a great job” heading off attacks, but there are limits to what can be done.

“You could do many things, and you stop 90-something percent of planned attacks, but miss some,” Bellino said. “I’m happy nothing has happened. Yes, I do worry about it, but I’ve got regular things of life to worry about.”

A soft target is any place that is largely unprotected, unlike a military installation, an airport or a courthouse. Soft targets can include schools, shopping malls, theaters and sporting events.

Americans have seen what an attack on a soft target can look like. A gunman in body armor killed 12 people in a suburban Denver movie theater in 2012. But the killer was a mentally ill American graduate student with no political agenda.

New York Mayor Bill de Blasio told the first 120 members of a new 500-officer-strong counterterror unit on Monday that the city “is the chief terror target in the country,” and daily vigilance is needed.

The New York Police Department’s counterterror units can now respond to as many as two dozen active shooting situations at once, having learned from such tragedies as the terrorist attacks in Mumbai, India, in 2008.