The whole Billy Barlow phenomenon - and that's what it was - is so complex that it can't be explained briefly. I've been reasearching it for about 10 years now. I came up with a book of my findings. It contains many of the connections between the hundreds of "Billy Barlows" of the 19th century. Also it tells the stories of ones I believe were key "Billys". (Sam Cowell, George Coppin, Robert "Billy" Barlow, and others)

I've never been able to establish a connection between Sam Cowell (or indeed any other "Billys") and the American Let's go a-Huntin/Billy Barlow. I do believe that Sam Cowell may have introduced it to America but I've never found the documentation. I've speculated about how it might have come about.
Cheers, Joy