Here is my $.02 and that is only my opinion so please read it in the spirit of light entertainment:
I believe that the American Market is a tougher one. First, the American consumer has the mentality of "satisfaction guaranteed or your money back." I have never heard that in Europe. I might be wrong, but my experience was, "if you do not like it, tough luck." So American conusmers complain a lot about quality and features and so on and so forth (and I am one of them.
) So manufacturer role the keyboards in other countries before the US to make sure that bugs are ironed out and that the American market is ready.
Second, American consumers look into specially the best features for the lowest price. In one sense, every person is like that... but that is specially true in American consumers. We ask the question, why should I pay this amount for this list of features. We buy keyboards from different stores to save few bucks. So in order for manufacturers to make profit, they consolidate the selections in the USA.