I currently work in online marketing covering Search and Affiliates. I would like an event that will both educate me and build new contacts in the US as I am currently UK based. I am swaying towards Adtech San Francisco or possibly an event in New York.

Adtech is a good choice and see if you can stay on for a few days and go to SMX at Long Beach.

SMX events are fantastic for networking http://searchmarketingexpo.com/social/