It sounds like you've already read the info on the USAT website, but I'm pasting it below for everyone else's benefit. I'm in the same situation after a race this morning and am curious to hear what the answer is.

From USAT website:
What is the Qualification Period for 2017?
The qualification period for 2017 Age Group Nationals began on July 14, 2016. The qualification period will end eight days before the event occurs on August 12, 2017. Registration will close eight days before the event occurs or when the event sells out (whichever comes first).

What is the Qualification Period for 2018?
The qualification period for 2018 Age Group Nationals will begin on July 7, 2017. The qualification period will end eight days before the event occurs on August 11, 2018. Registration will close eight days before the event occurs or when the event sells out (whichever comes first).

I raced a small sprint on 7/8/17 and placed 1AG but the results haven't been posted, yet. It'll be interesting to see which notification I receive. I suspect their notification system can't handle the overlap situation. I'd wait until after the Omaha races. If you don't receive a within a reasonable time, contact USAT and I'm sure they'll straighten it out.

RD's have 15 days to post results so it could take a bit to see the email from USAT. I qualified last weekend at Life Time in MSP and would rather go to Omaha than Cleveland. With the short window and needing to make travel reservations, I emailed USAT and they confirmed the results and got the invitation to me a couple days later.