Wales and the Welsh people had a huge impact on the founding of the United States and the American Revolution. Wales was England’s first colony, and the Welsh have been oppressed by the English since the Saxons first arrived in the 400s AD. It should thus be no surprise that the Welsh were among the original immigrants to the Americas, my own family included, and fought in the  American Revolution.

Thomas Jefferson writes in his autobiography that “The tradition in my father’s family was that their ancestor came to this country from Wales, and from near the mountain of Snowdon, the highest in Gr. Br.”

Other founders with Welsh ancestry (some only rumored) include Roger Williams, founder of Rhode Island and its religious freedom, William Penn, Sam and John Adams, James Madison, Patrick Henry, Benjamin Franklin, and Benedict Arnold and up to a third of the signers of the Declaration of Independence (http://www.flint.umich.edu/~ellisjs/Davies.PDF). William Penn actually wanted to call Pennsylvania New Wales.

Personally, I find this unsurprising, and it explains a great deal about the willingness of the founders of the United States to stand up to England.

One key to whether or not a name originates in Wales is if the last name is a ‘first’ name (e.g. Adam, Madison, Henry, Arnold, Jefferson, Williams). https://hisdoryan.co.uk/american-presidents-of-welsh-descent

A very common such name in Wales now is “John”. Another less well-known founder, Richard Morris, was dubbed the “Financier of the American Revolution” by George Washington.

http://www.data-wales.co.uk/namex.htm; http://freepages.genealogy.rootsweb.ancestry.com/~chrisandhowellsfam/howellstp_wales_contrib.html

The rationale behind the Declaration of Independence reflects strongly the letters written in November 1282–400 years before the Declaration of Independence–by Llywelyn ap Gruffydd, the last Prince of Wales, as well as his Council, to King Edward of England. These were written only a few weeks before Llywelyn was lured into an ambush by Edward’s men and assassinated:

From Llywelyn:

The realm of England may well be the special object of the Roman curia’s affection, but the aforesaid curia has yet to learn, and must learn, and the lord pope likewise, what evils have been wrought upon us by the English, how the peace formerly made has been violated in all the clauses of the treaty, how churches have been fired and devastated, and ecclesiastical persons, priests, monks and nuns slaughtered, women slain with children at their breast, hospitals and other houses of religion burned, Welsh people murdered in cemeteries, churches, yes at the very altar, with other sacrilegious offences horrible to hear. …

We fight because we are forced to fight, for we, and all Wales, are oppressed, subjugated, despoiled, reduced to servitude by the royal officers and bailiffs, in defiance of the form of the peace and of all justice …

Always the justiciars and bailiffs grow more savage and cruel, and if these become satiated with their unjust exactions, those in their turn apply themselves to fresh exasperations against the people. To such a pass are we come that they begin to prefer death to life…

From the Council of Wales:
The people of Snowdonia for their part state that even if the prince desired to give the king seisin of them, they themselves would not do homage to any stranger, of whose language, customs and laws they are utterly ignorant. For by doing so they could be brought into perpetual captivity and barbarously treated …