Unfortunately, I can't help you with how to obtain that from the embassy, but I did recently open an international (Canadian and UK) account with HSBC. A lot of documents were required, but not an authenticated copy of a passport. They have the same requirements to open an account in the US as they do in Canada, so with HSBC, you wouldn't have to have that. It did take about 2 hours to set everything up in the branch, but it was really easy to do, and they seem to be the best bank for people who need international accounts.
If you want to keep an account in the UK and be able to easily and cheaply move money back and forth, I'd recommend HSBC. I linked my accounts and can look at them both online at the same time and make instant transfers between the accounts. I'm not sure if there are HSBC branches where you're moving, but if there are, you should look into it, because they also transfer your UK credit to your US account, which really helps.