There's a myth that in 1794 the American House of Representatives voted, by just one vote, against making German the national language of the USA. Myth it is, but the notion that the most powerful country in the world is just another manifestation of a white, northern european culture is a one favoured, at least by white northern europeans.
Today just 79% of the USA's population is white. 13% are black with the rest of the population made up of asians and native americans. Moreover, projections for the mid 21st century suggest a white population of less that 50%. And along with the population change has comes social change.
The two world wars of the 20th century played a major part in kicked the change into action. The first world war created a huge demand for manpower in the industrial cities of the USA.The cities of the Northeast, Midwest and West took manpower from the first place it could find it - the agricultural economies of the Southern United States, the old slave states. Until then the 'freed' slaves had been agricultural workers largely in poverty. Industry went looking for workers and offered free train fares to people willing to move.
In 1910, the African-American population of Detroit was 6,000. Migration from the southern states rapidly changed this. By 1929, the city's African-American population had increased to 120,000. The run up to the second world war triggered another step change in the movement of the blacks away from the agricultural southern states to the industrial cities that needed the manpower. Present day Detroit has a black population of 590,000 82% of the population. As the black population took on jobs in the industrial economy they steadily gained ground socially. Education and increased affluence created a black middle class. Moreover, the newly affluent had larger families.
And the demographic mix continues to change. Trends for the next 50 years predict more asians and hispanics. According to: us-population-projections-2005-2050 This model predicts almost 30% of the population hispanics by 2050. And, by then, a white population of 47%.
The British conservative press frequently whines about multiculturalism, as though this has been something dreamt up by liberals intent on political correctness. That same press tends to look towards the USA to see the future. It will need to get accustomed to something it doesn't seem to like - a USA that is multicoloured and multicultural, and by golly, with whites in the minority.