No way that’s going to happen here.Sometimes other competing airlines will honor a ticket out of professional courtesy.
You might check other airlines flying out of BA. e.g., Delta, United, Ar. Ar.,LAN, Copa…
I did it once at the airline counter right at the airport but that was years ago.
Leaving aside that it happens very rarely in general, it’s also the case that all airlines here are swamped with people looking to rebook.
The final destination is not really the issue.Also you might have to alter your final destination.
Instead of SFO or SAN you might have to settle for DFW or MIA and then find alternate transportation.
There is no real problem with domestic flights, you’ll get a connection pretty easily.
The problem is a flight from Argentina to anywhere in the US.