Quite agree - in fact many so-called Americanisms are truer to the language of Shakespeare's day than the English equivalent, for example trash for rubbish and fall for autumn - some English pronunciations and words "froze" when they reached America.
Indeed, and I've often remarked upon the other benefits associated with American use of our language. Joshua Webster who compiled the famous Webster's American Dictionary was a far better scholar than our Dr. Johnson could ever have hoped to be, producing a consistency and rationalism denied to us.
In modern times they have often been more rational than us. For example, we incorrectly use the verb "lift" as a noun where the Americans correctly use the noun "elevator". If lift is our preferred root, we should of course describe the vehicle that accesses building floors as a "lifter".
I do think the source of criticism is often common usage pronunciation, and George Bush junior is a good example of this. He apparently is a citizen of "Amurcur" and introduced the dreadful "nucular" to the language, this promptly adopted by his poodle Tony Blair who had always correctly pronounced the word as "nuclear" previously.
However, I fear that this contribution to the thread might prompt Brian to think me a pedant!