Originally Posted by JJeffrey

When connecting domestically on AA to an international flight you do not have to re-clear security at any AA gateway in the US. You literally get off the plane, walk to the next gate, and get on the international flight, just like you would on any normal domestic flight.

And your covid docs will be checked at check-in at PHX. There's a small chance they will want to see them again before boarding at the gate in CLT but this is not the norm.

At CLT a 45 min connection is perfectly doable in this case, although it admittedly doesn't leave a lot of room for error if things were to get delayed. You will most likely arrive into the B or C gates and depart from the D (or maybe A) gates to FRA. Any of these gates can be reached within a 4-8 min walk or so depending on which gates and how quickly you walk and navigate your way through the crowds.