customs at Haneda

Hello!
I'll be flying out of Haneda to Hong Kong after a week in Japan on April 2. I plan to take the Keikyu bus from Shinagawa Seaside. My flight is at 8:55am, and the bus is scheduled to get there at 6am, 6:30, or 7am.

Any advice on how early to get to the airport so I can get through customs? Also, any experience with the Keikyu bus? Do I need to give myself more time in case of traffic?
Not sure if it makes a difference, but I hold a US passport.

Thanks in advance!

You don't need to go through customs on departure.
But you will need to get through security and immigration before getting to your gate at least 30 mins before departure time. Saying that - international departures at Haneda are fairly painless and I think 2 hours is more than enough and still leave time for breakfast/shopping. There shouldn't be much traffic at those times and it's a fairly short journey.

haha, mixed up customs and security. Thanks for the answer!