It’s the other way around. Current pronunciation in the UK was ‘affected’ during the 1800’s, just like french was ‘feminized’ during the 16–1700′s. While the USA and Canada preserved the germanic. If you listen to reconstructed Edwardian or Elizabethan, it sounds like a mixture of Scots and American pronunciation.
American whites were 50% german. We forget that while we share english language and english institutions, beginning in 1830 and expanding thru the Disraeli years, England ‘ceased’ being an extension of germanic-nordic civilization and evolved into a bridge between them and the French.
Americans are still more ‘German’. And pronunciation isn’t the only thing. We still work hard…. 😉