FPV drones, aside from EW and directed energy weapons, don't have any counter at the tactical scale (although fielding shotguns might help). Any counter will need to be infantry section/platoon scale to be effective, or at a minimum company level weapon system. The range of the AA countermeasure for an FPV drone will be on the order of 500m-1.5km, so covering a 1000s of km long front line is near impossible with current systems.