Let's play a little tactical/strategic wargaming, shall we? Let's say the UN does start dropping 'peacekeepers' in to end the 'Civil War' and 'maintain order'. Just where are they going to be?
Cities? UN troops go into high crime areas of cities like LA or Chicago. The gangs would have a field day. APC would have concrete blocks dropped on them from high-rises, sabotage, shootings, mobs, you name it. Eventually the 'peacekeepers' would end up in protected enclaves and 'safe zones', areas that had low 'gun crime' to begin w/. Gangs would then have all that equipment (real machineguns, FAL's, night-vision and other optics, possible heavy weapons and armor) they stole/looted from the retreating blue helmets.
Suburbs? Probably the only areas the UN could function. Lower levels of firearm ownership (legal or illegal), low crime in the first place.
Rural? Yeah right. How many hunters, target shooters, etc. would take shots at convoys or patrols as they attempt to move along highways and country roads? Potted blue helmets would replace deer heads on many a wall. One thing that several Europeans have told me is that the size of the US is hard for them to imagine since most of their nations are the size of one or two of our states if that.
So basically just another ignorant anti-gunner thinking he's qualified to make decisions on topics he knows nothing about.

