Excaliber beat me to it.

I have to question how a Block II M4 could be seen as not the "latest and greatest" or "locally sourced" in South America when only the United States uses that configuration.

I blame Cool Gun Syndrome instead.

I think we've made comments about that but also why Pedro Pascal's rifle only had the rear sight and no front sight. I understand if it had NO iron sights, but I don't see any advantages of just having the rear sight present. They kinda drop the ball on that one. Ben Afflek's M4 is pretty reasonable. It's pretty basic with an older EOTech

You wanna take screen caps of the guns and put it on the site?

I guess they figured that because it uses a Picatinny quad rail instead of a modular rail (Keymod or M-LOK), and an ACOG rather than some type of LPVO, it's not exactly the "latest and greatest" (basically, state-of-the-art for 2009, but not 2019). Even though obviously, IRL, the Block II-style M4A1s are still standard-issue for most U.S. SOCOM personnel, since the Geissele URGI and the new Nightforce and Vortex scopes haven't been issued yet.

On another note, ever since I saw the movie, I've wondered whether that M4A1 Block II is a Colt rifle retrofitted with a RIS II, or one of ISS's Daniel Defense M4A1s (the ones that they bought originally for "Sicario" in 2014-15) retrofitted with Magpul furniture. After seeing this video, I now believe that it is in fact the DD rifle, because around 11:33, you can just see the white laser markings on the left side of the receiver, and the flash hider also looks like a DD-style flash hider.

EDIT 12-15-19: In case anyone cares (or wants to add this info to the movie page on IMFDB), I've learned that Garret Hedlund's M4A1 Block II from this film is a Daniel Defense M4A1 upper on a Noveske N4 lower. The upper is indeed taken from one of the "Sicaro" weapons. Charlie Hunnam's M933 is also built on a Noveske N4 lower (also, the upper was originally acquired for "Transformers" in 2007, which is probably not a huge surprise).