Looking at the picture of the lady which accompanies the article, I would guess she is a bit 'high profile'. I know there is a bit of resentment in the UK against Bush Baby apparently dragging us into the Iraq fiasco, but that is to be expected. There are also older people who still make pointed remarks about how long it took the US to join in the 39-45 war.
A few, and I mean a few Americans are a bit loud wherever they go, the 'Everything's bigger in Texas' sort of attitude, but they are probably obnoxious at home too. This can cause resentment too.
Your average American can be a bit thin skinned though, and find the robust Brit humour hard to take, especially the irony bit which a lot of Americans don't do!
Methinks the lady doth protest too much, is my reaction to the article.
As for Maryrrf, I have met that nice lady, and nobody in their right mind would be rude to her. What's more she has good taste in choosing the nationality of her friends ☺
Giok