I'm not sure whether you can do what you propose.
One of the seven basic qualifying requirements for citizenship is that the applicant intends to continue living in the UK. However, as you indicate that you intend to return to the UK you may be justified in applying before you go to the USA.
However, if you look at this page :
http://ukinusa.fco.gov.uk/en/passports/ ... -documents
it only seems to envisage a UK or BOC birth certificate as proof of your citizenship for first-time passport applicants. Perhaps they don't mention a certificate of naturalisation because they never expect to see such an application, but that doesn't mean it isn't legal. Maybe it is linked to the requirement of continued residence in the UK, so they wouldn't do it - (but it wouldn't be for them to judge your right to citizenship, you would have already got it)
I don't know whether anyone else has a better idea.
Why not get your naturalisation, apply for your Brit passport and get the US visa in that?