I saw this movie at a pre-screening followed by a Q&A with the Director and Producer of the movie.
What a lot of people suspect here is 100% correct per the Directors and Producers own admission. They changed Taylors first draft of the script significantly, specifically the third act. In my opinion, this definitely shows. The movie was not in line with Taylors other epic screen plays, and it felt like the third act was completely missing.
If I recall the details of the changes correctly (which btw they were very proud of), they said Taylors original script had the third act culminate with BDTs character searching out the cartel boss, and continuing his rampage from the first movie. Instead, the Director determined the focus should be on character development. So the focus was shifted to BDTs relationship with the girls character, and they completely rewrote the ending.
The Director also did not see the relationship between JBs and BDTs characters as a friendship. He wanted to have them face off and go head to head in the movie instead of working together, resulting in the strange way JBs character made the phone call to BDT to basically tell him they are enemies now. They also apparently took out significant storylines related to the terrorists, and instead resolved that storyline by saying the terrorists were actually US citizens.
If anyone has any leads, I would love to get a chance to read the original script. I have faith that Taylors original ending was much true to the story and the characters.