There are a good few Star destinations but do many Star flyers actually connect over AMS? All of those destinations can be reached via most if not all other Star gateways.

In any case new AA service at AMS would obviouisly be for O&D rather than connections at the AMS end. It's worth noting that BA has a very large presence in AMS which feeds into the TATL JV so they will have good data on whether there is enough demand to satisfy a new non-stop.