US Regional winners are eligible for a reserved spot at worlds. Are there also reserved spots at US Nationals for regional winners? I know you get a bye but if you haven't already registered can you even enter?

Nope. They fumbled that one a bit since it's being held at Gencon, thus why they gave regional winners free guaranteed entry to worlds. Though keep your eyes on Gencon's site for tickets turning back up.

That is less than optimal. I hope they do something a bit different next year and hold spots for regional winners.