Great fares from Denver (DEN) with Delta and from Atlanta (ATL) with United for tickets to Hong Kong for just $536. Note they each have that fare only from the airline's hub.
Many dates are available in the next couple of months.
You can book the fare on Expedia.com or on the airline's website (if you want to use gift cards!)
To make it even cheaper, consider a multi-city search and fly from ATL or DEN and return from PVG (Shanghai) instead of Hong Kong. Shanghai is a great city and easily the most interesting in China. No visa is needed if you spend just 72 hours or less in the city and have an onward ticket.
If you don't like United Economy so much, you can fly on ANA for $579 as well. Use Kayak.com to search.
You may even be able to route via Guam and the 'Pacific Hopper' but I could not price it on this level.