Anyone can write wikipedia, those statistics could be made up. Although its a prodominatly white, there is many different people of different races and religions all around the city. Racisim hasnt really been much of problem to my friends of different races and the people who do hold racist viewpoints tend to keep to themselves rather than put them into practice.
I have seen plenty of Koreans and people from all over the globe at Newcastle games, I would be very suprised if you encountered any problems there.
As for the American accent bit you should be okay if you dont start chanting 'DE-FENCE!DE-FENCE!DE-FENCE!'