The real reason Citizens need guns

In reality could US gun owners put a militia together that could ever topple their federal government and if not then what's the point on the 2nd amendment?

I graduated from West Point, Ranger School, Airborne School, Air Assault School, and the Counter Insurgency Academy (among many other schools). I also did three tours in Iraq as an Armor Officer. I led soldiers from the platoon level to the company level. The entire time, I fought an insurgency that was drastically outnumbered, outgunned, and out everything else,t you could imagine. Our forces were the most technically advanced, best equipped, best trained fighting force the WORLD HAS EVER SEEN.

But we never defeated the insurgency. The Iraqis we fought were poor, ill-trained, ill-equipped, mostly uneducated, yet we couldn't defeat them. They basically had old rifles and pistols, AK47s, homemade explosives, and old military munitions like 155mm artillery rounds and mortars or whatever they looted from the Iraqi Army when it was disbanded.

Now imagine an insurgency of Americans. Highly educated (by comparison), with many times the financial resources, many times the physical assets(vehicles, tools, etc) armed with similar rifles to what the military uses. All the jet fighters, nukes, tanks, battleships in the world are nothing against a determined insurgency.

Also there are thousands of veterans who fought against the Iraqi insurgency who know all the tricks. I was on tanks myself and I know how to take them out. I know how to make homemade explosives. I know how the military taps phones. I know how they set up networks of informants. I know how they plant fake munitions that kill the user. I know the tricks. 

Thousands of people like me know the tricks. You don't even need that many people to conduct an insurgency. The big advantage is time is on your side in an insurgency. You can watch twenty patrols drive past you and do nothing. You decide when you are going to strike and you can't be drawn into a fight for which you are at a disadvantage. You just wait for opportunities. You go about your normal routines and quietly watch and note the patterns of the military you are fighting. 

Eventually, you will see a weakness like hey the patrols always go over this one bridge at 5pm, so why don't we rig the bridge to collapse when they are driving over it? Or hey the Colonel's vehicle is always the third vehicle in the convoy and has these distinctive markings so let's have the roadside bomb destroy the third vehicle and cause as much chaos as possible. Or the expensive helicopters always fly through this valley after dropping off supplies so let's mass our fires on them and try to take one down.

We never defeated the Iraqi insurgency completely. I was in the last brigade in Iraq. We drove out to Kuwait (because the airstrips had already been shut down). We were shot at on our way out.

The answer to your question is yes a militia of gun owners could win against the US government. It's been done before.