Ok let me try to summarise the thread so far
1)Cops are a deterrent, but they are pretty useless except for clean ups. Just note: In cities with strict gun controls, cops do have guns as well as other non-lethal weapons like tasers. In Japan cops train in Judo and Kendo many hours a day so that in case of an arrest, there is no need to fire upon the suspect (innocent or guilty).
Solution? Fitter cops who have to undergo mandatory fitness tests like the military, martial arts training, non-lethal weaponry for regular crooks (rubber bullets, riot shields, tasers)
2) Criminals do use guns, So despite 64999 gun owners not committing crimes, crimes are committed with weapons that are made to kill people.
Question: If it came down to it, would you have guns removed from all citizens and criminals and left in the hands of the authorities, or have a anyone can own a gun policy?
It is much easier to run away from a man with a knife than a man with a gun. If Colombia was besieged by a pair of knife wielding madmen, would they have been stopped easier?
3) Which leads to the next question. Is a citizen's revolution possible? The Police, Military, Coast Guard, FBI, Secret Service all own weapons, are better trained and have better weapons. The only way to overthrow a corrupt government would be for the military to act on it, then it would either be a revolution or a coup d'tat.
Would you attack one of the uniformed guys on the other side if it came down to it? What if some of them are on your side? SWAT vs Delta Force? Which side is right, which side has the constitution on their side?
4) One thing I would agree on, it would be very hard for a country to invade the US using conventional forces.
But suppose I was invading the US and there were pockets of resistance everywhere. I would make a simple ultimatium.
"If you do not surrender, we will nuke a city every hour"
So it's basically back to an arms race, your pistol/assault rifle/tanks/planes/bombs vs theirs