Not quite sure "how" the Ponthieux name arrived in U.S., however, records I have indicate that the name can be traced back to Northern France. In France it is spelled Ponthieu, even to this day. I have some genealogy records on the Ponthieu/Ponthieux family in Louisiana. My paternal grandmother was a Ponthieux, but I can't get verification of her parents, therefore, I can't trace my tree back beyond her (born in 1883).
If you have any info on the Pontheiux family, I'd love to share.