I don't see anything in NPT that forbids the US and UK from supplying nuclear propulsion to Australia. They are not supplying nuclear warheads.
The reason the French are pissed are strictly commercial. But that is on Naval Group. As soon as the deal was struck between Australia and Naval Group, Naval Group were changing the terms, and were years behind on some of the earliest deliveries. Had the project been going well, Australia would not have spent political capital seeking this new deal.