Europe is full of different dialects. And English has been consistent for about 500 years. We can read Shakespeare with almost no trouble.
But those dialects have been stable for many centuries, the official language for newspapers and study purposes is a compromise that was developed so that those very dialects can still communicate with each other. I know this to be true because I speak German (high German) and French, but I also know 2 regional dialects of German and one of French. The dialects are very stable indeed. You are making an assumption that they all started from a common point and then adapted in different regions but actually all the regions were developing independently but also borrowing from each other during their very formation. The common language came later, not before. I would also say that reading old texts in German is easier than reading old texts in English. I would strongly dispute your contention that it is easy to read 500 year old English. Middle English and Early Modern English is very hard to read. Even Herman Melville (Moby Dick) gives a lot of people trouble - mostly because of vocabulary rather than grammar, but even some of the grammar is tricky. I think you are just assuming from hearsay that what you say is correct because nobody who has studied Middle and Early Modern English would say that it is easy to understand. I would even dispute your claim about Shakespeare; a lot of people who read Shakespeare see a word and assume that it carries the same meaning as a similar word in modern English.
Example: Wherefore art thou Romeo? Almost everybody I ever meet uses this wrongly. They think it means "where are you, Romeo?", when in fact, "wherefore" means "why", as in, Romeo, why did you have to be called Romeo? Meaning, why did my love have to be from the Montague family - the sworn enemy of the Capulet family. This happens all the time with Shakespeare period writing - similar looking words with different meanings, often known as "false-friends".
Recently, there has been a shift in German though because they have introduced a lot of "cool" words from English into their language. Which disturbs me a bit because they tend to use them incorrectly and it pollutes their language. The French are the opposite - they will do anything to avoid foreign words from polluting their language. Good for them, I say. I much prefer speaking German without English words in it - it makes me cringe to see how they use them.
Ok, lecture over now...
