Factual error: The Marines that arrive at the landing site are said to be from El Toro, but El Toro was a Marine Corps Air Station; it would not have had the infantry, artillery, and armored units that arrive at the site.
Factual error: A remarkable error. Late in the movie there is a shot where extremely large, perfectly round blood-stains are shown on the street as soldiers are shown giving chase to the wounded monster. These ignore basic physics. Whilst the source of the blood may be huge, individual blood drops would not have been proportionately larger.