What you are doing is imagining there to be some sort of abrupt ending of England's influence and the beginning of America's influence on the English language ~ which we share with them.
We still have people who grovel at the sight of the Queen of England.
BTW, as best we try the English still have some influence on the shared tongue ~ probably always will have.
Sir, just get a copy of the 1887 Webster`s dictionary and go to page 532 -you will read the definition of middle class=
“middle class -In England,
people who have an intermediate position bewtween the nobility and or
leisured class and the working class. It includes professional men, bankers,
merchants, and small landed proprietors.”
No such similar “middle class” exists in the United States which does not a have nobility.
My family was around-
BTW my family has been here since 1648 and my great grandparents, my grandparents, my parents, all never uttered those words to to me in their lives. They would say “down and out”, “in the poorhouse”, etc. but never say a worded phrase such as lower class or middle class- It was foreign to them because, indeed, it is a FOREIGN PHRASE OR TERM, does not apply to the USA, only England, from whence it came.