The NC and PA Alexanders are the same family. The place names you mention are all along the MD/PA border. They attended The Rock Church, formerly in PA, now in MD. Some went south to NC and became the Alexanders of Mecklenburg fame, the others migrated in western PA. You will find a great deal about them by contacting the Cecil County Historical Society.
You will also find them in the History of the Rock Church, and also in Johnston's History of Cecil County. The Cecil County Public Library has several copies in circulation so you should be able to borrow it through interlibrary loan.
The border between PA and MD was disputed until the line was drawn by Mssrs. Mason and Dixon in 1767. New Munster Tract was mostly in MD, but extended about a mile into what is now PA. PA's claims extended into MD, and MD's claim extended fifteen miles in PA; you may find documents issued by either state as a result. The area roughly corresponds to the Fair Hill Natural Resource Area today.
Anyone researching families in this area should consult New Castle Co, DE; Cecil County, MD, and Chester Co, PA, and possibly Lancaster Co, PA.
The Alexanders were a numerous clan, and lived on both side of the (modern) PA/MD line.
I am a descendant of Abraham Alexander Sr, who chaired the Mecklenburg Convention, but I am not an expert on the Alexanders. There are numerous books and documents about these families -- I have done most of my research in the Cecil County Historical Society, and I know that I have not tapped out the Alexander resources there.
This family originally arrived c. 1665, Somerset Co, MD, then migrated north, and were probably among the 'fifteen other Irishmen' for whom the New Munster Tract was surveyed in 1683. You will find them as ministers, blacksmiths, elders, and so forth in the various Presbyterian Churches of this area.
I have not yet heard back from the Presbyterian Historical Society, in Philadelphia, PA, that is another source to check since these Alexanders were all Presbyterians.
I have been offered varying parentage for Abraham Alexander, Chair of the Mecklenburg Convention, I would appreciate hearing from anyone who can give me solid information on his parentage. Thank you.