Of course the 2nd Amendment is about individual citizens. Why would they have needed to amend the Constitution to allow our military to bear arms?
Your individual RKBA is protected by your state constitution. Which is why gun laws (eg., concealed carry) vary from state to state.
Think about it. If the second amendment protected that right, the laws would have to be the same in each state, would they not?
The militia is not the military, any more than the posse is the sheriff or police. Both are US, that is "the people".