"But the troops in the video are U. S. Army soldiers from the 1st Infantry Division."
Well, I don't know about the "all", but I watched it again and on those soldiers where I could make out the left shoulder patch, it was that of the 1st I.D. as you said. I was 11 years a commissioned officer in the army reserve, and I am familiar with most active and reserve division insignia. I don't have a clue what type of "divisional" patches a Marine would wear.