How would the reception be in London, or the Isle of Man? We're planning to visit some day, as somewhat of a personal thank you to your nation.
I think that the residents of the Isle of Man would be friendly to American visitors, but I can't really advise you about the best parts of London to visit, as I haven't been there in the last 18 years. However, Ivan lives down in London and so if he is not too busy at the moment, (he has been getting a lot of replies recently - like 500 today already), then he may be able to tell you if there are any areas of London - or specific places in London - which visiting Americans should avoid.
If you were to visit York or Newcastle upon Tyne then I'm confident that you would be well received as I have spent 11 years in those two cities. (Although, be careful walking around the city centre after 8PM on Friday and Saturday nights, since there are always a lot of drunk and rowdy people on the streets during those periods).
I'll just confess I'm an Anglophile.