When viewing the action thriller “London Has Fallen,” there’s no escaping the reality that you’ve seen everything on the screen before — many, many times. For every bullet, and you will lose count, there is a cliche.

It’s not that the by-the-numbers film is unwatchable, and all movies borrow from the past, but “London” sets the bar low for creative inspiration. This lack of originality should come as no surprise, given that “London” is the sequel to “Olympus Has Fallen,” which was already tired when it came out three years ago.

Where “Olympus” laid siege to Washington, D.C., the latest adventure leaves the British capital in ruins, thanks to terrorists who can kill heads of state and blow up well-guarded landmarks with the flick of a wrist. The considerable wreckage makes the work of the aliens in “Independence Day” look amateurish.

There to save the day, though, is Secret Service agent Mike Banning (Gerard Butler), whose default personality trait is kick-ass. Before being dispatched to London, Banning is on the verge of hanging up his Secret Service boots, as is required in worn-out screenplays. Naturally, an attack of world proportions occurs, and Banning can’t reunite with his expectant wife, because he must protect endangered U.S. President Benjamin Asher (Aaron Eckhart), whom the terrorists want as the star in their new beheading video.

The film hopes to woo us with its CGI effects of bombarded London and Banning’s gunbattles with an army of terrorists, but they come off as perfunctory. As usual in American action films these days, it’s hard to decipher what’s going on during the ferocious firefights; we just watch and wait patiently (or impatiently) as the body count piles up.

Director Babak Najafi tries to whip up some fun banter between Banning and the president, but most of the time Butler and Eckhart can’t pull it off. These actors look physically similar, and when they’re together they cancel each other out. Most of their problem is bad chemistry: Eckhart’s temperament seems more suited for a football coach than a head of state, and Butler consistently falls flat when he tries to deliver a droll line. It makes you appreciate the skills of Bruce Willis in “Die Hard” or Kiefer Sutherland in “24.”

There will be few films this year that squander such a formidable supporting cast. Morgan Freeman, who has portrayed convincing leaders in the past, seems to be channeling his chauffeur from “Driving Miss Daisy” instead of a resolved vice president. He’s the last to arrive in the situation room, and apparently missed all the awful developments on the TV news.

The performances of Melissa Leo and Robert Forster appear to have ended up on the editing floor, with a total of about three unmemorable lines between them. Another great actor, Angela Bassett (slumming it), is a nonfactor, too. But that’s probably a good thing for these thespians, because the more screen time that actors get in this film, the worse impression they make.

The briskly paced “London” has one thing going for it, or against it, depending on your point of view. It feeds on the nation’s current fears about Middle East folks and about the level of terrorism threats within our borders. The producers have made what they intended to make: a paranoid, patriotic popcorn movie.