Back in those days, people didn't go back and forth between states as often as this guy would have if he were one and the same person.
Regarding the two different birthplaces for Abraham (Sankt Gallen, Switzerland vs. Stuttgart, Germany), consider this.Save the Bible record, on this side of the Atlantic, there are no documents that link Abraham Barrier (son) to Michael Barrier (father).Michael Barrier died without a will, and Abraham doesn't seem to show up on anything in the U.S. that reveals his parentage.I think that the christening record found in Germany is a record for another Abraham altogether.(Maybe this Abraham Barrier born in Germany also came to the U.S.?)
There are many different variations of Barrier (Barringer, Berger, Barger, etc.).It wouldn't surprise me if there was another Abraham Barrier born at the same time in Germany with a brother of the same name.I've seen this personally in my own genealogical research.For example, (names changed to protect the innocent), I've seen two Elva Uriegas who were born 5 years apart in the same town.Both girls had fathers named Raul Uriegas, and both girls had a sister named Antonia, who were also nearly the same age.But the two Elva Uriegas were *not* related!One family had been in the town for generations; the other family were recent immigrants.
Just because someone found a christening record for an Abraham Barrier in Stuttgart, Germany, with parents Michael and Katherine and brother George Henry, doesn't mean that it's the same Abraham.All these names (Michael, Katherine, George) were very common, and there are a zillion variations of the name Barrier.