The phenomenon could tap into a growing group of nonbelievers in the United States.
According to Pew Research Center's Religion & Public Life Project, there has been an increase in the number of American adults who say they seldom attend religious services and those who do not identify with any religion at all.
About one-fifth of the public overall -- and a third of adults under age 30 -- is religiously unaffiliated as of 2012, according to Pew Research.
Fully a third of U.S. adults say they do not consider themselves a "religious person." And two-thirds of Americans -- affiliated and unaffiliated alike -- say religion is losing its influence in Americans' lives.
About 5 percent of all Americans say they do not believe in God or a universal spirit, but only about one quarter of these nonbelievers actually call themselves atheists.
One, Roy Speckhardt, who is executive director of the American Humanist Association, likes the idea of the Sunday Assembly, citing its "technology, entertainment and humor."
"It's not like what we have done before with weekly lectures and a gathering lunch afterwards," he told ABCNews.com.
"Our meetings are mostly academic and somewhat social. That's nice, but it's not quite the community atmosphere that you get in a modern church today. [The Sunday Assembly] has taken pages from of the book from the new churches in the Northwest top get their message across."
"The megachurch environment is the highest level of entertainment and not just a weekly moment with your pastor -- it's much more structured than that. It's working in a big way in the UK and could definitely work here, too," he said of the Sunday Assembly.
The American Humanists do "good without a god," he said, and are an advocacy organization in science, politics and legal work.
Speckhardt agrees that the Sunday Assembly could tap into the large group of nonbelievers in the United States. But, he warns, "Atheists are a tough group to get together for a lot of reasons. … [They] have been burned by the religious environment and don't want to do church-like things."
But many nonbelievers "could come out of the woodwork later if a certain critical mass is reached," he said.
Speckhardt points to other Pew studies that show one third of Americans "connected to their faith" do not believe in God.
"They are ripe for this," he said. "If 1.5 Catholics are not sure there is a god, that's over 500,000 people. There is a mind-boggling potential."