Lexington Green was a tactical mistake. Under 100 militia standing in line (who weren’t actually expecting to really go into combat) against 700 British regulars whose entire modus operandi was, well, standing in line and firing by ranks - not brilliant. However, most figured out that this was a bad idea and fled before they took many casualties.
However, Concord was another matter entirely. The outnumbered British troops got hit by a numerically superior militia force and they ran like hell despite light casualties.
After that, some Americans stopped playing by the straight-up European battle rules and did what we’d consider common sense these days - they ambushed the Brits from cover and concealment, sniped at them, and basically refused to fight by the ‘rules’ that favored their opponents with usually favorable outcomes. Others gathered in large groups and fought conventionally with mixed results. The British fled, bleeding and staggering, all the way back to Charleston, MA.
Moral of story - don’t play by your enemy’s rules.
You shouldn’t knock down the field tactics of the day so much. It was the time-tested, best way to get a volume of fire on a target. The best you could do firing from behind trees was spray and pray, comparatively. Moreover, firing from concealment was what would today be considered terrisn or bushwhacking.
Morgan at Cowpens.