Masterbeato, you are invited, so long as, at the time of your registration you are one of the top 5 rated Amateurs from your state and your rating is based upon the minimum required rounds, no matter when those rounds were recorded.
Through the years the qualification requirements for Am Nats has varied and truthfully, I have never kept close track. Nor did I consult the website this year or have in-depth discussions with the powers that be (because I was too busy with the round at hand) but to date, the event has never filled with pre-registrations. However in the few days preceding the event, on-site qualification rounds have placed many competitors in the field. Basically, if you can shoot a round rated at 915 or above, and a spot remains, you are in. The course, however, is a demanding, unforgiving challenge know as the Toboggan. All you need are power and accuracy and nerves of steel. Occasional brilliance never hurts.
As more questions come in I will try to be a conduit for semi-official answers.