No, that is completely false. At the time the F-100s arrived (1991), I believe the largest aircraft Eagle had was the ATR. Regional jets weren't even considered for Eagle, plus AA
knew the F-100 wouldn't work on an Eagle cost structure.
Also remember that at that time, Eagle wasn't one carrier. It was just like the United Express or Delta Connection family.... American Eagle was just a banner under which numerous carriers flew (Nashville Eagle/Flagship, Simmons, Wings West, Executive were the big ones... I believe Metroflight was still around at the point when the F-100 arrived).