Appears that there's no way to have AA honor EC261 rules then?
According to EU law, passengers should have the choice between one of the following:
(a) - reimbursement within seven days,
(b) re-routing, under comparable transport conditions, to their final destination at the earliest opportunity; or
(c) re-routing, under comparable transport conditions, to their final destination at a later date at the passenger's convenience, subject to availability of seats.
I'm in the same boat as OP. AA has cancelled the LUX - US fare (since BA doesn't fly to LUX til June), but AA only offered me +/- 1 day change from e.g. FRA instead LUX.