Lovecraft You should get a partial refund but nothing under EU261 as it wasn't a flight to or from an EU destination nor was it on an EU airline

Whilst EU 261 applies to all airlines leaving from the EU it only applies to registered EU carriers when flying into the EU.

So e.g. two flights from JFK to LHR are delayed by 5 hours - one by BA one by AA. EU261 would apply to the BA flight but not the AA one (even if the AA one is a BA code share)