Update:
My understanding is that as the schedule change is signifcant (3+ hours), EU rules say I am entitled to a refund (as one option). Not compensation,

I called AA twice. Each time I was told that as the itinerary originates in US, EU rules don't apply.
Surely this is incorrect - the schedule change is for the ex-EU leg, and my understanding is that EU rules apply to all ex-EU flights, whether or not it is an EU airline?
Note - at this point, the aspect of potentially cheaper alternate flight no longer apaplies.