StatGuy2000 said:
Part of the reason I'm curious about this is because the United States is often described as a "land of immigrants", but if one's roots in the country date back before the massive immigration waves in American history (during the 19th and 20th centuries), they may not consider themselves to be descended from immigrants (whether that is accurate or not).
If they have European, or even African, ancestry, they are descendants of immigrants. BTW, immigration was more or less continuous from Europe and Africa (forced in most cases) from the 1600s on.
I'm curious about the OP question. Why not ask if "What % of Americans have colonial roots?"
Forty-five of the 102
Mayflower passengers died in the winter of 1620–21! My wife is related to five passengers on the Mayflower: John Alden and Priscilla Mullins (married 1621, both 8th great grandparents), Priscilla's parents (William & Alice Mullins, who are 9th great grandparents), and John Soule (10th great grandfather). William & Alice Mullins, and Priscilla's brother Joseph Mullins, died in February 1621.
John Soule married Mary Beckett (or Buckett) who arrived on the Alice and Little James in 1623. Apparently, some of the immigrants from the Alice and Little James were sent back to England after they were deemed unsuitable for the environment. We do find some records to be inconsistent.
https://en.wikipedia.org/wiki/List_of_Mayflower_passengers_who_died_in_the_winter_of_1620–21
http://mayflowerhistory.com/mayflower-genealogy
Most of my wife's ancestors are English and French Canadian and Dutch (father's side) and Irish, England, Germanic Eu (mother's side). She related to the first governor of Rhode Island and some of the early presidents.
I'm a more recent immigrant (mid 20th century). My ancestry is mostly Scottish, English, Germanic Eu, Norway, Wales, Ireland, Sweden/Denmark, although a different genetic testing company put me more Scottish/Irish/Welsh/Scandanavian/Finnish/Aegean (Greek and S Italian) and Ashkenazi Jewish. Go figure.
Although I wasn't born in the US, the majority of my existing relatives live (and were born) in the US, followed by England/Scotland/Wales, Australia, Canada, NZ, Ireland, Sweden, Netherlands, Germany, France, . . . . I've also identified relatives who have African and Indigenous (North and South America, Australia, NZ, Pacific Islander), and some with a combination aforementioned groups. Some US relatives go back to 1600s, some 1700s (New England or Virginia), some during the 1800s, and a few more recently in the 1900s. Some relatives moved from US to EU countries, where they died.
Many of my ancestors were farmers, miners or labourers, some were merchants, and back in the 1500s-1600s, some had estates, which were lost during the English Civil War. One of my paternal ancestors was an Archbishop of Canterbury, which tickled my father (clergyman) and would have tickled my paternal grandfather (clergyman) had we known before he passed 20 years ago. Along the way, I've found relatives who died in WWI, WWII, Korean War, and others. I have a 3rd great grandfather who died/disappeared at sea near Sulawesi Tengah, Indonesia in 1841; I don't have the details.