The truth is, the belief that a few millions gun-wielding Joes could take down a government protected by well trained, well lead, and loyal army is outright silly
Not true at all.
One of the biggest things it keeps alive is an attitude of self-reliance as it pertains to force that can contribute to a population with a mindset that has the will to win.
Those firearms themselves are also not all it takes, directly taking on formal organized forces in any standoff is a losing proposition as they will then coordinate and bring their greater resources to bear.
Groups of armed men clustering together will easily be taken down, especially from the air.
They also have developed equipment to tell the direction one is firing from to eliminate snipers in Iraq, something sure to be employed by modern nations in any future rebellion.
IEDs, improvised artillery, and other indirect methods are required to attack better equipped modern forces.
However firearms do help when cornered, or to assist explosives in ambushes.
A very key difference in an insurgency or civil war from say recent conflicts in Iraq or Afghanistan is that the economy that provides the money to support the military is hit harder at home than when they are deployed abroad.
This means in a civil war the economy generating the tax dollars funding the well equipped forces suffers, and over time can no longer support them.
You don't see this in a war abroad because the economy is not being destroyed from within by war. So the tax revenue the military depends on is not impacted.
But when there is extensive disruption in the militaries own nation, things are different, and they have to start getting outside economic help just to stay afloat.
However at the same time some civilians start starving, and things get really ugly. All families would be seeing an impact some much worse than others before it got to the point that the government was collapsing from lack of tax dollars.
You also start getting people loyal to the insurgency joining the military, and attacking from within, seen even in Afghanistan today where they try to screen out such people with the help of capable intelligence agencies.
A few guards that turn their machineguns inwards here and there really creates havoc and destroys morale and soldiers start wondering who the next soldier to turn and kill them will be.
Beyond guns the population can make anything. The IRA was making its own mortars from basic things for example:
http://en.wikipedia.org/wiki/Barrack_buster
Various groups in the middle east launch relatively easy to build rockets fitted with warheads in mass at enemy forces on a regular basis.
These are also indirect fire weapons.
Now a civil war or insurgency is certainly not something you want to see. In fact it is a primary tool for defeating nations today by others. Just look at the strategy in Afghanistan today, training 'security forces' to battle the former government and its supporters. It is essentially outsiders using the population against themselves to defeat the enemy. A key role of special forces for quite some time, locate people not loyal to the enemy, and turn them into fighters against your enemy.Done in most modern conflicts, and quite extensive in Vietnam and other extended conflicts.
There is also very few people as noble and selfless as George Washington, that go from leading the opposition military forces, being chosen as the head of the government after victory, and then stepping down on their own or willingly without consolidating power and become a tyrant worse than what you had before. He had the backing of the military he led, and was popular with the people. So he could have stalled and consolidated power and undid pretty much any brand new framework that was not really established that he wanted to.
Many men in the same situation just become the new tyrant.
So even the most noble of revolutions is just a roll of the dice as to what will happen even if won. Sometimes you get a France situation where they guillotined many people, and kept suspecting new people of things and killing many in prior leadership positions out of paranoia.
Or the purges as done under Stalin after Lenin died and that government founded in a historic peoples' revolution took a very dark turn in a direction far different than what had been envisioned to become ultra authoritarian.
Peaceful methods are always the ideal method of change, but a well armed people are definitely a force to be reckoned with.