In reply to:

While generally speaking, i don't consider the US to be part of The Commonwealth countries, we do share:
language

Yes and no. In many, if not most, Commonwealth countries English is neither the official nor the majority language.

It is not "an exaggeration" to say that the US is part of the Commowealth, it simply wrong. The Commonwealth did not exist until after WWII, nearly 200 years after the US had left the clubhouse. The date is not open for one to pick as you state - The Commonwealth came into existence on a specific date. Prior to that, there was no "Commonwealth of Nations" for any country to be part of.