You are talking about conventional warfare, line ‘em up and shoot it out. I doubt we would ever see that unless large parts of the military defected- like entire military facilities, I cannot imagine that ever happening but would make a good book/movie theme. Unconventional war is a whole different thing, and has been quite successful in the past against large well armed forces. We might see something like that at some point.
Unconfentional war has been successful, but at tremendous cost.
The Geneva Convention requires combatants to wear a uniform recognizable at a distance, and to separate themselves from noncombatants and avoid targeting civilians, hospitals, churches, schools.
Only through the violation of the Geneva Conventions have unconventional combatants been successful.
The Geneva convention specifies that when illegal combatants do not separate themselves from noncombatants, they do not thereby gain protection, but rather protection is removed from the noncombatants. The rules are written that way so that combatants have no incentive to put noncombatants at risk. Damage to noncombatants when combatants illegally colocate with and hide behind noncombatants is the responsibility of the illegal combatants.
Combatants have a choice with the US military: (1)Surrender, (2) Be destroyed, or (3) Try to hide behind noncombatants. Option 3 leads to massive casualties among the noncombatants, casualties that are legally the responsibility of the unconventional warrior.