Welcome to Flyertalk, Ro_Laren. The rule of thumb, for split itineraries, is:

If you're connecting in the same airline, they'll check your luggage through.
If you're connecting in the same alliance, they'll try to check your luggage through.
If you're connecting to any other airline, you have little more than a vague hope.

There are some other exceptions (point-to-point fares on legacy airlines that specify no connections - BD are famous for this) but that's the way it usually goes. So, if you connect AA-AA, you'll be fine; BA-AA, you have a good chance; VS-AA, probably not.

OTOH, AA and VS both use T3, so at least it's an easy connection. You would have to go through immigration and customs if you need to collect your bags.