Nope sorry she is on film stating such. In fact I think its in one of the Films extras "making of Harry Potter etc." type video on the DVD where she states that even though he is an American... not that he was going to make the film Americanized but because he was an American.
Your attempt to portray her as antiamerican isnt going to wash, sorry. I have seen such interviews as well (although I am NOT a ‘Potter-ite’).
When she says American, you see that as her showing disdain as a pompous Limey for he being an American. Full stop. But thats wrong. You arent understanding what she said.
What she actually meant by ‘American’ was American=Hollywood=Hollywood ruining her story. And I have seen her explain this in interview.
Rowling didnt and probably still dosent like Hollywood and the many base and stupid films/blockbusters they produce, and she had horror at the idea what they would do to her stories. Which is why she fought to keep the stories as they were.
She has gone on record as saying she didnt think Chris Columbus was at all the right choice, as he was known for rather silly films like Home Alone and its sequel or Nine Months. Very Hollywood, very American and very forumlaic.
She promptly admitted she was wrong after seeing the first film.
You are seeing her bashing America, when in fact all she was unhappy about was Hollywood.