If you mean the classical liberalism of the founding fathers as being Protestant, you are correct. If you mean that Protestant Christians are progtards, you ignore that evangelical Protestants are the most right wing religious group in the United States. Meanwhile the cafeteria Catholics here in the northeast ain’t exactly right wingers or devotees of the founding principles of this nation. Of course cafeteria Catholics produce agnostic and atheist children and “devout Catholics” are a tiny minority as well.
Lots of American Catholics are functionally Protestant in all of their religious and philosophical assumptions, but owing to the disgraceful state of Catholic education, they don’t even know it.