I sometimes think the same is true of language. The first American settlers were immigrants too, and in some ways they too hung on to the old (linguistic) ways.
Take the past participle (third form) of ‘get’ for example. Those of you who are students of BrE (the form of English used in the UK ,and its cousins in Australia, new Zealand etc), will of course know that it is ‘got’. But in AmE (US English) the form ‘gotten’ for certain meanings of get, like become (gotten married) and obtain (they’ve gotten a new car), is also commonly used. Although not for possession (I’ve got the answer, not gotten). Now this usage used to be quite common in British English as well, and you can see lots of examples from Shakespeare and from the King James Bible (still the most popular version), both from the early 17th century. But somewhere along the way, for us, it has dropped out of use. You can read more about this and other grammatical differences between BrE and AmE in great detail at Wikipedia. A writer at the (UK) Spectator who was criticised for using gotten, quotes in his defence the American writer H.L.Mencken on the use of got and gotten, and about how the preterite (past simple) and past perfect were almost interchangeable in Shakespeare.
This is not to say, of course, that Americans have not contributed to the development of the English language. Far from it. They simplified the spelling system for starters and although I prefer my BrE system out of force of habit, it is hard to argue with the logic of the US system.
And 20th century American writers gave literature in English a new vitality, cutting away a lot of the verbosity, to concentrate on the narrative (story).
Nor is AmE static. For example, students of BrE are taught to use Present Perfect with words such as already, yet and just. Now in AmE you will often here the Past Simple used instead, eg: I did it already. As the Wikipedia article points out, this use is fairly recent.
But in some ways I find AmE grammar more rigid than in BrE.
I once came across a blog written by, I think, an (American) advertising copy editor. It included a text which had twenty errors you had to find. Well I got up to about 17, and for the life of me couldn’t see any more, so I gave up and looked at the answers. Well two of them I kicked myself for not getting, but the last one was not, in my eyes, a mistake. And in fact the second sentence of this paragraph contains (quite accidentally) the same ‘mistake’. - Can you see anything wrong with that sentence?:
It included a text which had twenty errors you had to find.
No? Good! Neither can I. First question - what grammatical structure do we have here?
We have a defining relative clause, sometimes known as a restrictive relative clause. Can we change the word ‘which’, and if so what to?
Yes we can. We can change it to ‘that’. Now mainstream BrE courses for foreigners teach you that you have a choice. That while most native speakers will in fact say ‘that’, it is also quite correct to use ‘which’. And this is the case in UK English. But not for many Americans, and this lady marked it as a mistake.
The copy editor's old bugaboo about not using "which" to introduce a restrictive relative clause is also an instance of failure to look at the evidence. ‘Elements’ as revised by White endorses that rule. But 19th-century authors whose prose was never forced through a 20th-century prescriptive copy-editing mill generally alternated between "which" and "that." (There seems to be a subtle distinction in meaning related to whether new information is being introduced.) There was never a period in the history of English when "which" at the beginning of a restrictive relative clause was an error.
And just one last difference. In the comments section of another blog, a contributor was gently pulled up (see 4) on his grammar for saying something like:
The University climate team have just published a new report.
Can you see the problem?
The noun team is Singular, while the verb have is Plural. This breaks the rule of formal agreement where every verb should agree with its (or is it their, perhaps?) subject.
And just to finish off I’d like to recommend the marvellous The Best of British, ‘’The American’s guide to speaking British”, written by Mike Etherington. There’s a lot of stuff here which was new to me too.