I can't speak for South Korea or Japan, but for Australia and New Zealand (until 1986) they were more or less tied to the US' apron-strings.

In 1951 Australia, New Zealand, and the US signed the much anticipated ANZUS treaty which extended US military protection to Australia and New Zealand, and in return Australia and New Zealand promised the US support in their military endeavours. This is why Australian and New Zealand troops participated in The Korean and Vietnam Wars. If we take those wars as setting precedent, then the Australian-New Zealand plan would have been to supply troops and allow the US to organise logistics, attack plans, etc.

In 1986 New Zealand was suspended from the ANZUS treaty because the government refused to allow access to nuclear-powered US ships. The US was unprepared to say which ships were or were not nuclear powered and so all ships were barred entry. As a result the US revoked its pledge of protection.

As of today, as I understand, the dispute has been 'resolved' but US nuclear-powered ships are still barred from New Zealand, and the US offers New Zealand no military guaranteed protection.