"You just had the most horrific school shooting and now you are forcing states that want to ban guns in certain ways from doing it."
How does your system of government work at the most fundamental level? Here we have constitutional government, where the highest law in the land is a written and not easily amended document. Oh, and it's the birthday of the primary author of the opinion, who's been more and more strident about the Supreme Court allowing the courts below it to nullify their previous decisions a dozen plus years ago.
"What happened to states rights?"
Like the right to keep slaves? See the 13th Amendment to the Constitution. (We can tell you're not an American or are a young one because you don't know the #1 connotation of "states rights" from the civil rights era.)
"I also don't see how not allowing conceal carry prevents you from bearing arms when 'the government is coming to get you'."
It makes all sorts of gambits more expensive. Look for videos of subjects of the PRC being vanned and never heard from again. The shades of 100 million killed by their own governments in 20th Century tell us this is by far the most important reason for a Right to Keep and Bear Arms (RKBA), but it's hardly comprehensive, there's such a thing as lethal force used by criminals to defend against.