Thanks for your perspective. In the case of the naturalizations, the writer was a U.S. government employee who did not have an Irish last name and who was probably a native English speaker. His handwriting was polished. He was probably reasonably well-educated though perhaps unfamiliar with Irish county names. This leads me to believe he wrote the county name as he heard it. Reading the earlier discussion that said that certain Meath accents would make the word sound more like Maid or Mead caught my eye since it mentioned speakers from Navan as an example. This fit nicely with the other early records I've found linking the family to nearby Stamullin and Drumcondra. It seems like there is a reasonable chance that my ancestors pronounced the county as Mead, adding a small bit of evidence to the idea that they were from somewhere near Navan -- unless this pronunciation is widespread throughout Meath or perhaps even into Westmeath and/or Roscommon. Pronunciation aside, I'm starting to put more weight in the early records that mention Mead/Meath since they were generated for the individuals themselves by government or clergy. The records mentioning Westmeath and Roscommon relied on informants who gave info for deceased family members many years after they left Ireland.
