There are two main arguments used to oppose any new restrictions on guns in the United States. The first is for home self-defense. While there are undoubtably some instances in which a home owner has been able to defend himself from a criminal using a gun, there are far more instances where having a gun in the house has resulted in the homicide, suicide, or accidental death of family members living in that home. Gun nuts may not want to admit it, but having a gun in the home is far more dangerous for family members than it is for criminals.
The second, and much more ridiculous, argument is that the guns possessed by ordinary citizens may someday be needed to oppose and overthrow a government that has become too tyrannical. This argument ignores the fact that those privately-owned guns would be pretty useless against a government with the most powerful military in the world -- a well-trained military that possesses tanks, planes, drones, missiles, bombs, rocket-propelled grenades, artillery, and other modern and very lethal weapons. Our military may not be suited for nation-building, but it would be very effective in putting down an armed rebellion.
But there is an even better point to be made here -- that when the people no longer support a government, that government cannot survive. And guns are not needed to topple that government. There are many examples of this in modern world history. Consider the example of India. In 1947, India threw off the yoke of British rule and became an independent nation -- and they did it non-violently (without using guns). And that is not the only example.
We also have the examples of the Marcos dictatorship being ousted in the Philippines (1986), communist dictatorships being overthrown in Poland and Hungary (1989), and the fall of the Soviet Union (1991). Guns were not needed or used in any of these examples. The truth is that when enough of the population of any country no longer supports the government, that government cannot survive. As Boris Yeltsin said, "You can build a throne out of bayonets, but you can't sit on it very long."
A tyranny will exist only as long as the people allow it to exist. That is a fact. And when enough people no longer support it, guns will not be needed to topple it.