Thank you for all your responses. I do have travel insurance which will cover the cost of the ticket in full however I would still like to explore opportunities to change the date if possible as this was one of the cheap J ex-OSL to US tickets from last year. For clarity, I am happy to let this ticket go in the circumstances but I was interested to explore options before jumping.

I spoke to the BA ticket desk at LHR yesterday and they were able to remove the flight BA segments but leave the ticket open. I then spoke to AA on the phone this morning and was told that they do not cancel non-refundable tickets, instead they leave them open - took him 35 minutes on hold to come back and tell me that.