2) Nuclear weapons are the only physical weapon that can check the US Government. That's why they shit their paints when a basically inconsequential country such as North Korea launches a potential nuclear rocket.

3) In the 1700s guns were the best weapon of the time. Nuclear weapons did not exist. Civilians were able to own basically military grade weapons and could theoretically rebel and potentially win.

4) In current days, if you wanted to legitimately make the claim of government check on power with civilian weapon ownership, you'd at least have to argue for military grade, fully automatic weaponry ownership rights by civilians. Not to mention the ability to stockpile explosive weapons and missiles. A bunch of civilians with gimped semi-auto ARs and hunting rifles would have been the 18th century equivalent of the right to bear bow and arrows or pitchforks and shovels.