The three original American dialects — New England, Mid-Atlantic and
Southern — all had their origins in different areas of England and
reproduce many of the characteristics of those areas. The varieties of
Southern English, as well as the Midwestern twang, evolved in consequence
of these dialects' rubbing together.
Non-English dialects have had relatively little influence, except in
semantics and several structures which are clearly marked as non-English
in origin (for example, Yiddish influence in the New York area; Black
English influence). Languages in contact (as opposed to dialects in
contact) rarely interact except in extremes and never in phonology.
Rather there may be borrowings, which are eventually integrated into the
target language (corduroy, diapers, etc.), or else one language
obliterates the other, as in Latin taking over Gaulish, or English taking
over Irish. However, the latter case is special, since traces of Irish
remain in phonology, familiar syntax, and vocabulary. A standard form
evolves when a group speaks such a mixture of dialects that no particular
one can be distinguished.
The principles are the same for any language which `emigrates,' as with
English, French, Spanish and Portuguese into North America. First the
emigrant languages start to evolve from a specific homeland dialect. Then
they evolve differently from the homeland because of lack of contact. The
less contact, the more different the evolution, because the home dialect
also continues to evolve.
The U.S. kept less of a `British' accent because it threw off British
dominance at a rather early stage, which Australia and New Zealand did
not. The educational system in those countries continued to import
teachers and administrators from "home," as the British linguistic model
was considered `superior'. Canada is an odd case: it is also
British-dominated, but the Maritimes, which were the center of Canada for
a significant while (from 1755 until around 1830), were heavily populated
with Celtic groups, both Irish and Scots, who emigrated to get away from
the British, or were expelled from Britain, and did not particularly want
to follow a `superior' linguistic model.
A large group of American Loyalists went to Canada after the Revolution
and settled en masse in southern Quebec and southern Ontario, bringing the
already-evolved U.S. linguistic model. This model continued to be
powerful because of the constant contacts between Canada and the U.S., as
opposed to either country's contacts with Britain. Upper-class speech in
Canada sounded vaguely British (to U.S. ears, not to British ones) until
around the 1950's, when it aligned itself with the American model, keeping
only certain particularities in pronunciation (individual words, not
phonemes), structure (lack of articles, as in "she's at university") and
vocabulary. It is practically impossible to distinguish a Western
Canadian from a Northwestern American, because both groups moved west
around the same time, with a resultant mix of dialects.
All emigrant languages tend to be linguistically nostalgic, preserving
archaic forms of pronunciation: the `hillbillies' really did preserve
forms of English which date back to Shakespeare, although what they
do with those forms is another question.
Many of the "distinctive" phonetic features of American English are
in fact from the British Isles. The feature that most Americans (and
some Canadians) recognize as distinctively English is the nearly
silent final 'r', making "water" sound like "watuh". This pattern
is characteristic of a dialect triangle formed by Cambridge, Oxford
and London, and of areas to the east of that triangle. The same
pattern is found in areas of the U.S. and Canada which were settled
by emigrants from eastern England, such as Boston and Plymouth.
The final 'r' that we associate with American English is quite distinct
as a kind of growl produced near the back of the mouth. This sound is
standard in the west of England (Shakespeare would have growled his final
'r' sounds), in the north (Wordsworth and the Brontes) and in Ireland.
Most of the British settlement in North America in the nineteenth century
came from the north and west of England and from Ireland (especially the
six northern counties of Ulster). This emigration provided the dominant
settlement and the dominant dialect features of Ontario and of the
mid-western U.S.
As for the German component, German settlement in western Ontario and
both the eastern and mid-western U.S. was heavy enough that German was the
second language in these areas. Much of the religious, social and
economic fabric of these areas is German in origin. The German sociologist
Max Weber studied the Germanization of the growing American cities,
especially in the mid-west, in "The Protestant Sects and the Spirit of
Capitalism." The American novelist Sinclair Lewis studied similar features
in his novels without specifically tracing them back to German roots.
Linguistically, the German influence probably reinforced the clearly
articulated final 'r', added some lexemes to the vocabulary, and added a
lot of German family names. German last names seem to be as common in
positions of power in the United States as Scottish names are in Canada.
At one time President Nixon's advisors seemed to be nearly all German by
name.