The world is under attack from mysterious aliens again, and someone has got to do something about it. Twenty years after an American president, played by Bill Pullman, led his people and Earth to victory in “Independence Day,” the sequel has Earthlings fighting back again — with words of inspiration from the retired president and from a new commander-in-chief, played by Sela Ward.

Scenes from “Independence Day: Resurgence” received their first airing Thursday during 20th Century Fox’s presentation at CinemaCon, and exhibitors reacted enthusiastically to a sequel that Fox co-chairman Jim Gianopulos said “has everything you loved about the first film, but with the benefit of 20 years of new technology.”

The Earth now faces the menace of outsiders who can control gravity itself. When panic ensues, Ward’s President Lanford reminds her citizens they have been here before: “In their sacrifice we found the technology to build a stronger and safer earth,” the president says. “Our survival is only possible when we stand together.”

The Fox trailer does not reveal how Earth (presumably) prevails, but it’s safe to say that plenty of inspirational talks help get them there. When some weakling preaches that Earth does not have a chance, Pullman’s retired president has a ready retort: “We didn’t last time each other. … We sacrifice for each other no matter what the cost. And that’s worth fighting for.”

Still, national landmarks and entire cityscapes are washed away like the tide, before the locals rally.

Actor Jeff Goldblum explained that the long delay that followed the 1996 “Independence Day,” which set box office records for its day. The filmmakers “didn’t want to just do something else, they wanted to do something terrific, and they didn’t want to betray the enthusiasm and devotion of the fans from the first one,” said Goldblum.

Director Roland Emmerich told the crowd that making the film “felt like a class reunion, with some new like kids thrown it. It has been quite amazing.” And Ward promised “a delicious popcorn movie you cannot watch on your laptop or your telephone.”

Theater owners greeted that pronouncement, and the new “Independence Day,” with a rousing ovation.