I've never met anyone who said regretted leaving one legacy for another legacy. Usually they latch on to one or two things that they decide are important enough to warrant a move and double down on it.

If you live in base legacy Jobs are about 80% the same.
There would have to be massive structural changes at AA to make it anywhere near as close to United on the international front. The chances of AA funding and executing such a plan are close to zero. United on the other hand is attempting to rapidly grow and upguage its domestic network and is running into significant issues when it comes to aircraft deliveries as well as some other issues.

If your family lived in a podunk town in the USA there would be a much greater chance AA serves it 3x daily with one of its RJs than United ever serving it at all. If going to see your international family is important to you that's probably going to be facilitated much better by United service throughout your career.

Live within 2hrs of a United base that services your international family and your life should be pretty good.