The only thing eligibility gets you is the opportunity to win a US
Championship medal. Nothing more, nothing less. If you are a US citizen or
green card holder (and I'm sure you are), then there's absolutely no reason
to say you're not eligible. It's not like we charge you more.
ps -- no medals on the open courses, so it's irrelevant there.
Day 1 course setter
ps #2 -- USOF membership is different from championship eligibility, and for
that you get a discount on the entry fee. That's worth it!