I believe that your John Polk was a brother to my gggrandfather Charles T. Polk. Their grandfather William Polk and his two sons, William and John, entered America through Charleston at a date "antecedant to 1795". There is no direct connection to the Polks of Mecklinburg Co., NC. I would be glad to share with you what I have found, as well as what I suspect.
Please contact me directly at doriroy@wildblue.net