[NZerFromHK]

I had a look at the table provided here:

http://factfinder.census.gov/servlet/QTTable?_bm=y&-qr_name=DEC_2000_SF3_U_QTP13&-geo_id=01000US&-ds_name=DEC_2000_SF3_U&-_lang=en&-redoLog=false&-_sse=on

It seems that if I add "British", "American", "Scottish", "Welsh", "Irish", "Scots-Irish", "English", and unspecified ancestry (adjusting it by probability that they are German or Italian ancestry) together, it seems not more than 35% of all Americans have majority British/Irish ancestry. Not sure if my guess proves correct.

[cripplecreek]

I know that there were a large number of Welsh in my states (Michigan) upper penninsula at one time. Mostly miners from what I can find. I live in an area called the Irish hills, so I'm assuming there was a fair sized Irish population here. I'm German and grew up in a town named after Hanover Germany.

We were a pretty diverse european bunch here.

[Wallace T.]

If you assume those that identify themselves as American, United States, or White are mostly people of pre-1800 British Isles origin, and that about half of those who self-identified as Canadians had similar origins, then there are 92.2 million Americans who claim British Isles origin out of 225.3 million Americans who identified their national origin, 40.9% of those who identified their origin are English, Scots, Welsh, Scots-Irish, or Irish by ancestry. (The assumption that the self-identified Americans are mostly of British descent is supported by the concentration of these people in Appalachia, the Upland South, the Ozarks, and North and West Texas, where (except for Texas), there is little black or Hispanic population and little impact by the European immigration of the 1840-1920 period.)

Out of a total U.S. population of 281.4 million as of the 2000 census, about 115.1 million Americans have roots in the British Isles, assuming those that did not identify their national origin were equally distributed among the population.