"Well Regulated" is a strong descriptor you're ignoring.
I'm not ignoring it at all. None of that will stop someone from deciding to do something foolish. you will still have millions of Americans with guns, often the guns the left wants banned. Any of them can still snap and go on a killing spree.
But in this scenario it would have to go thru several court battles and establish a new precedent. The current precedent of court decisions goes directly against this. Possible but very unlikely any time soon (several decades imo)