Yeah, I love the musket example "Well, that's all that they had back then!"
Let's apply that logic to the 1st amendment - the only thing we can use is the Guttenberg printing press, quill and ink, and the town crier. No internet, computers, email, radio, TV, movies,...
Oddly enough I think conservatives would survive more easily than libs.
Regarding the Army issue, all men over 18 are essentially in the militia whether they know it or not if they've registered for selective service. Not exactly "well regulated" but they've taken the first step whether they know it or not.