If the SCOTUS has defined the 2nd amendment as an individual right, as I understand it, why are the privileges of that right altered by one's state of residence?
A longer answer is because we are dealing with concepts that were codified in the late 1700s, and the generally accepted meaning of the language used wasn't really challenged until the 1900s.
Why did it take until Heller for the high court to rule and say our right to arms was an individual right, independent of the militia?
Simply because there was never any need to do so, until the self proclaimed "progressives" decided that what the Constitution said wasn't what it actually meant, and substituted their views, instead.
The nature of our government, and its relationships with itself, the states and the people have changed, since the Founders wrote the Constitution.
We are a long, long way from "to provide for the common defense, to coin money, and to regulate trade between the states" that the Founders hoped would be the only roles for the Federal Government.
Understand that for a long, long time, the only "US citizens" were those citizens of US territories and possessions. Everyone else was a citizen of a STATE. And the states were, voluntarily part of the Union. Those concepts still exist, but we are a long, long way from them today, as a practical matter.
The Federal Government rules the nation, but allows states to pretty much do what they want, up to a point. And that point is a moving target, depending on the issue involved.
If a state gets to write their own rules, about SOME things, why not everything?? or nothing? There is merit to both arguments, and also in the system as it currently exists.
How much and to what amount such merit matters, depends on the number of people who's ox is being gored, on any particular issue.
Personally, I think the system isn't broken, and therefore, doesn't need to be "fixed" (and fixed badly) the way a small but very vocal minority are demanding.
Could it, and should it be improved? Absolutely, but I don't think the proper way to do it is with a top down federal mandate, whether its called a law, a court ruling, or something else.
Don't get me wrong, I grew up in NY, and hated the laws there, way back then. I would hate the laws there now even more, but I don't live there now.
So I have a strong belief that no one from the outside should tell the people who live there how to manage their affairs, just as I don't want someone doing the same to me.
The people who live there COULD change their laws. They can change the way their government applies their laws. If they cared to. Its called representative government. (sometimes called democracy)
The down side is that if enough people are bullheaded the same way about something, they get what they want, no matter if its the right thing, or not.