Wales never had an Independence Day, although it has been inching towards more autonomy for the last twenty years. Welsh people, however, had a huge impact on the founding of the United States and its revolution. Thomas Jefferson writes in his autobiography:
“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).
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). 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.
And then, if the Welshness of certain American influenced the American Revolution, according to John Davies, later Welsh-Americans returned the favor. He states:
“Welsh Nationalism was a concept born in Cincinnati, where Michael D. Jones was a Congregational minister in the 1840s. To be Welsh in Wales was to be from Carmarthenshire or Anglesey or Glamorgan or Denbighshire. To be Welsh in America was to be from Wales. Periodicals and newspapers in Wales were local- Y Gwladgarwr serving Aberdare and much of the south, Y Fanerserving Denbigh and much of the north and so on. Welsh periodicals in America served the Welsh in their entirety . . .
And not only were the Welsh as a nation invented in America. So also were almost all the causes that have been central to our endeavor over the last two centuries.
As Gwyn Alf Williams has shown in his brilliant books on Madog and Beulah, late eighteenth century Welsh radicalism, religious as well as political, was largely borrowed from the American Enlightenment. In the early nineteenth century, the temperance and teetotal movements were directly inspired by the American example, and the leaders of the movement to disestablish the Anglican Church in Wales looked to the American separation of church and state as their model.
The victory of the North in the Civil War was interpreted in Wales as the triumph of a democratic people over a decadent landed aristocracy, an inspiration to those who launched an attack upon Welsh landlordism in the 1870s and 1880s.
The 1880s also saw the emergence of a republican movement, much to the distress of Queen Victoria. Thomas Gee, the editor of Baner ac Amerserau Cymru, described republican rallies with enthusiasm. American flags were carried, he noted, and the crowd shouted the names of American Presidents.”