When Chavez and his squad are going to be inserted covertly into Colombia, the fact that they use M16 rifles is mentioned, along with that their identification and other clues to American origin were removed.
Since Colt has been very careful licensing companies to manufacture M16s, the M16 is a clear symbol of American origin. Had they chosen AKs or H&K submachine guns such as Chavez has, their nation of origin would be hidden. Instead, the M16 marks them as Americans as clearly as if each man were carrying a large US flag.