When traveling back to the USA from Canada, all the customs formalities are done in the Canadian airport, before one even sets foot in the USA. My Global Entry accreditation that I did for my trips to China is still valid (it is $100 for 5 years), and it came in handy today. I could bypass a very long line at the passport control by scanning my passport, looking into the camera, and providing four fingerprints. I was very tired, and the flights felt very long : one to Denver (3 hrs) and one to Seattle (3 hrs).