[Puffer Fish]

The United States is not really ethnically homogenous. If you go to different regions of the U.S. you may find that the people seem very different, in a way that is difficult to put your finger on exactly. A big part of this may be because of the differences in the gene pool. Even among the white population, depending on the place settled, people came from different origins in Europe.

In this map you can see "largest white ancestry group in U.S."
https://i.pinimg.com/736x/df/85/06/df85 ... 8dd178.jpg
It pretty much delineates the outlines of "The South", who now mostly all specifically consider themselves "American" ethnicity. In most of the rest of the country, German was the main contributor to the white gene pool.
In a small but very highly populated area around New York City and New Jersey, Italian is the biggest ancestry group for whites.
The New England area got much less German influx, probably because this area was already settled by the time German immigrants came.
Lots of Irish in Massachusetts and eastern parts of upper New York. There was a big wave of Irish immigration in the 1840s and later Italian immigration around the 1900s, when poorer immigrants were moving into the big city areas. This explains why 67% of the Christians in Massachusetts today are Catholic. Cities in the South didn't need Irish immigrants at that time because they had black slave labor. Later when the Italians arrived, the economy of the South was still in recovery from the Civil War, and the South had a lot of black poverty and not many Italians were needed. A few were brought to Mississippi to help harvest cotton but were treated half like blacks. The poorer white areas of the upper South did not welcome them.

You can also see that only the northern third of Florida is part of "The South". The southern part of Florida was too hot humid (air conditioning came later), often had hard limestone poor soil or was swampy, so didn't get settled until much later. The city of Miami, today very important in Florida, was not founded until 1896, late in the country's history. The "culture" in southern Florida is more like the Midwest.


In this map you can see that the people in "The South" have mixed English and Irish ancestry. Actually it might be more accurate to say Scotts Irish, since the majority of the whites in the South came from poorer areas in Britain further north. The wealthier plantation class in the deep South came from further south in England, and owned slaves, so for the most part these areas became part of "The Black Belt", with the exceptions of Charlston and Savannah whose wealthy economy relied more on commerce and trade.
(recommended further reading: "American Nations: A History of the Eleven Rival Regional Cultures of North America" by Colin Woodard)
The map also show Hispanics from Mexico now make up the majority of the population in the Southwest quarter of the country.
https://pbs.twimg.com/media/EIo53JkWwAMYGJP.jpg
These Hispanics have mixed European and indigenous blood from Mexico, but have less European ancestry than the average in Mexico. Their European ancestry more largely includes Spanish and Italian than in the U.S.

In addition, you can also see some French ancestry areas in Louisiana and sparsely populated U.S. areas right across the border from Montreal and Quebec City in Canada.
Some parts of the upper Midwest have significant percentages of Norwegian ancestry, but these are sparsely populated and cold prairie farming areas.
Significant English population in Virginia, this was colonized early but did not really become a big attraction for immigrants later. Since it was already settled but never developed any big cities with opportunities. (Germans did settle inland areas of Virgina)


In this map you can see the "Black Belt", a sweeping area across the lower "South", where Black people make up the majority population.
https://coopercenterdemographics.files. ... orted1.jpg

This area often seems to get mostly forgotten about by the rest of the country, and the white population does not think about it. Few people visit or move there, and it almost gets treated as if it were some separate country. With the notable exception of the city of Atlanta. And maybe New Orleans too, which is remembered in American culture and tourists do visit, but at the same time is kind of half-forlorn. The high black population is half the reason it is like another country. The Cajun cuisine is the other half. The white population there is a mix of French, English, and poorer Scotts-Irish.

[Puffer Fish]

Southerners thought of themselves as "American" unless they had some family lore or information about their ancestry. That's probably because the south was largely ignored by later immigration waves. Italians, Poles, and so forth never went south, they went to northern and midwestern cities. So until the civil rights era made it okay to move south, the South was a preserved in amber view of pre-20th Century immigration America.

There were three groups in the South. English, who had come as the earliest wave. Blacks who were important for plantation agriculture. Here's a little interesting fact not many are aware of. Only about 388,000 black slaves were ever actually imported to the American South. From that small number, the black population rapidly expanded due to natural increase. Labor was very much in demand at that period of time. Many of the early waves of Irish immigrants that would come to the North later didn't have it much better than the slaves. But there was one big difference: the climate. Europeans did not want to work in the heat and humidity in the South, toiling out in the open fields. But the most profitable cash crops, tobacco, cotton, and corn (and sugar cane in a few places further south) grew much better in the warmer climate of the South. So they needed black labor.
The wealthy plantation owners, the gentry class of the South, were of English ancestry (and in a few cases French, in Louisiana and early St. Louis). But there were never very many of them of them compared to the black population in those areas. Georgia was considered "the heart of the South", and yet had a total white population of only 300,000 right before the Civil War.
In the "upper South", in states like North Carolina, Tennessee, and Kentucky, the demographics were very different, a much smaller black slave population, and mostly only concentrated into certain lower lying arears near the coast or Mississippi River. The white population in these areas, especially the more remote mountainous and less desirable interior areas, was settled not by the English but rather mainly from Scots-Irish settlers, who had slowly migrated down through the Appalachian mountains. The ancestors of this population originally settled in America in southern Pennsylvania, in very early times. As everyone knows, this population tends to have a very different quality and temperament than the English population. Poorer, less sophisticated whites, what often became considered "white trash". The tended to have more "fiery" personalities, be independent survivalists, and had a distrust of government (likely partly originating from the history of oppression the Scots-Irish experienced from the English, part of the reason that drove them to leave to America).
In the middle Piedmont region of North Carolina, up the rivers, many Germans settled, originally from the interior Shenandoah valley settlement in Virginia, and these Germans mixed with the local Scots-Irish population that was already there. This happened three decades before the Civil War.