> AUKUS involved countries already in NATO-like agreements with the US (UK is in NATO, Australia in ANZUS) so it doesn't really change much in terms of security alignment.

It does, because it pissed off France ( which also has territory in the Pacific) for no good reason, and also stated that the choice of nuclear subs is due to the Chinese threat. And also it pushed the delivery date of new Australian submarines by at least a decade, probably more.