OK! LEt me state that they are all the same.

1 - Gaelic song tradition, with the laments and such came to the US in the late 1700s through to the early 1900s. Each wave, from Scotland, Ireland, Man, Wales, brought forth more of the music, which we "classify" (however wrongly) as Celtic.

2 - These songs, tunes, and dances were brought over, along with the people, and they taught them to the people they found here, indigenes, black, yellow and other caucasians. Various groups embraced these forms, and enhanced them.

3 - The blacks and others took the Scottish/Irish step-dances and made it into the now famous American tap-dance standards. The same people took the tunes and songs of the Gaelic laments and blended them with the rhythms of their native lands, giving us the blues

4 - Country music is another "child" of the Gaelic song laments. If you took the themes of the Gaelic songs circa 1600/1700/1800, translated them, and added instrumental accompaniment, you would have the Country music.

5 - Out of the traditional music of the early 19th century, we find they grew into the "Folk" music, such as Appalachian, Ozark, and Arkansas regions have kept alive. Songs such as Red River Valley, and such have been found in the early 1800s. They are now part of the folk/country of today.

6 - The tunes, and uses of the OldTimey fiddle music comes out of the Scottish dance tradition, which again is part of what we now call "Celtic".

7 - Song tradition scholars have shown a definite relationship between the "recent" songs of the 19th and early 20th century, and songs/tunes from the British Isles or Europe, or even Africa. I am sure there are others with ties to the Mediterranean countries, or elsewhere. Would there not be music from Scandinavian countries in amongst those in Wisconsin? Probably.

 

This is just quickly off the top of my head. But I'm sure, with a little research, you can prove each and every one of the above statements, which I believe implicitly.