The Individual World Championships are open to any player who has an IPIN and is of the correct age (35+, 40+ or 45+). Singles, doubles and mixed are available for one entry fee. However, there are a disappointingly small number of American entrants in this event. The USTA does award USTA ranking points (normally the same points as for a Category I National, though I don’t know how many are being awarded this year).
The draws can be found here. Doubles draws aren’t yet posted but singles draws are posted now.