Wilkerson from Ireland to North Carolina, then back?

My 2x great grandmother Margaret (nee Wilkerson) Johnson was born sometime between 1810 and 1815, one of twins, in Chatham County, North Carolina, USA.  Her father had been born in Ireland.  Her mother died in childbirth, or very shortly afterward.  The family story goes that her father (given name unknown) returned to Ireland and took with him Margaret’s “red-haired twin sister.”  Nothing further was ever heard from my 3X Great Grandpa Wilkerson, and “Grandma Peggy” was raised by maternal relatives with the Copeland surname.  I’m guessing that her father’s reverse immigration would’ve occurred in about 1816, after conclusion of the Napoleonic Wars. 

I’ve found no marriage record between a Wilkerson and a Copeland, anywhere near Chatham County, that would match my long-sought-after 3X great grandparents; perhaps they were wed on the other side of "The Pond."  There’s more confusion, because the name might actually have been Wilkinson.  I don’t find any records of any Wilkersons in the Irish Republic, just Wilkinsons.  I do see Wilkersons in and around Belfast, so I'm guessing that is where I should be pursuing research into this particular family line.