What you arent taking into account is the ordinary armed citizen in the USA who arent the "Rambo" type. Rambo did not exist during the Revolutionary War, ordinary citizens did. The writers of the Second Amendment were ordinary citizens and they toppled the British control of the Americas.
An individual, as you term "Rambo" would do nothing against a tyrannical government, but as a group armed citizens can keep government in check if the will and means is there. You seem to want to take the means away.
Back in the 80s a Russian warship docked in Anchorage, a local was able to ask the captain how the Soviet Union would do in a land invasion of the USA. The captain wasnt concerned about the US military but as to how well armed the citizens are.
I think Ladys Human covered Switzerland,
Final thought, where have the most recent, the last 20 years, mass shootings taken pace in the USA?