The pronunciation of English has changed in both Britain and North America since the first English settlers arrived there. Hence different accents. Anywhere you get a language spoken in different areas which are not in close contact you're going to get different accents. Do you have regional accents of Hebrew in Israel yet? Even if you don't, I'm sure there were different regional accents in Biblical times.
This site
http://www.askoxford.com/asktheexperts/faq/aboutenglish/proportion?view=uk puts the proportion of present-day English vocabulary which derives from Old English and other Germanic languages as 25%. But these tend to be the most common words in the language. When the Norman French invaders foisted their language on us, we developed the habit of using French/Latin derivatives for more formal/learned/official contexts.
