Transformers: The Last Knight. Source: Paramount Pictures

Ever wonder why Hollywood keeps churning out 'Transformers' films? You're not the only one. With each new addition to the franchise, the reviews have gotten worse and U.S. audiences have waned. Despite the lackluster performances in the United States, two of the "Transformers" films have garnered more than $1 billion in total global ticket sales. The most recent 'Transformers' film, "The Last Knight," opened on Wednesday to lackluster results. The feature garnered $5.5 million from Tuesday night previews, and only $15.6 million on its opening day on its way to a franchise-low debut weekend haul of over $43 million. All the rest of the movies in the series have opened over $97 million. Even worse, it was widely panned by both critics and audiences. The film earned a score of 15 percent on Rotten Tomatoes, the lowest of the series so far.

Ahead of the weekend, the film has an audience rating of about 62 percent. However, while many critics have already had a chance to view the film, audience members will likely continue to weigh in over the weekend and that score could change. While the film has had a lukewarm reception domestically, international markets heartily embraced "The Last Knight." It took in $196.2 million internationally, including a whopping $123.4 million in China. Countries like China, India and South America have driven the majority of box office revenue for the "Transformers" franchise since the first film was released in 2007. At the box office the first two films in the series saw a pretty even split between U.S. and international ticket sales, but with each additional release, that gap has widened.

By the fourth film, "Age of Extinction," more than 77 percent of box office revenue was earned overseas, a whopping $858.6 million. For comparison, the film garnered $245 million total in the U.S., less than the opening weekend gross of "Star Wars: The Force Awakens." "U.S. audiences have been subjected to so many sequels over the decades that it is hard to maintain the excitement," Paul Dergarabedian, senior media analyst for comScore, told CNBC back in May. Dergarabedian attributed the film's international success not only to the action sequences, but the casting of Mark Wahlberg—an action movie star—and the fact that much of the film took place in a city in China. He said that international audiences like to see films set on a global stage. The "Transformers" franchise isn't the only one riding an international wave. The "The Pirates of the Caribbean" films have also been met by lackluster reviews and U.S. audience fatigue.