When you get back to the early 1800s or earlier it gets harder and harder to trace all of your lines because of incomplete records (except perhaps in New England), so many people may not know for sure how many of their colonial or Early Republican ancestors were English, Scottish, "Scots-Irish," Catholic Irish, Welsh, German, or Huguenot--a lot of the French and German names were anglicized out of recognition. A Scottish-sounding surname may be a clue but perhaps only the direct male line was Scottish and the rest was English or something else.
When I saw the heading I thought the thread would be about the ancestry of the counties as political units--that is fairly simple to figure out from the information in The Genealogical Helper about parent counties, but probably easier to find nowadays with Wikipedia. Not that anyone cares about that information unless you need to find out where some information would be located.
a lot of the French and German names were anglicized out of recognition.
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and Dutch names after 1664 when the English took over the Dutch colony of New Netherland without firing a shot and changed the name to New York..