Not sure how we could boycott US products effectively. They're world leaders in trade and business, and a lot of people don't realise how many pies they have their fingers in (including pies that used to be British). For example, I've not bought anything made by Cadbury's since it was sold off to Kraft (a US company which owns so many companies that I couldn't list them all here).
Examples: Kraft dairy products (of course), Nabisco, Jacobs, Oreo biscuits, Maxwell House, Philadelphia cheese...
When you don't know where they are, it's hard to boycott them. They don't necessarily make their products in the USA, they just own companies here and cream off the profits. But this is the great global market that so many people wanted, so now here it is, merry Christmas.