Presumably. Aussie citizenship is part of the process:Whilst I get the extension to other Commonwealth realms, who are technically in a form of personal monarchical union, and whose militaries largely share traditions and configuration. However from my reading (as below) US citizens could not be an officer, without losing US citizenship.
"And that's why, also, from the first of January 2025 we'll be allowing our Five Eyes nations, people that are in Australia, permanent residents, from the Five Eyes nations of the United States, the United Kingdom and Canada, to be able to apply to join the Australian Defence Force. They will need to meet the normal enlistment requirements in the ADF, including security vetting, they will need to have been a permanent resident in Australia for at least the last year and not been a member of a foreign defence force in the prior two years. They will join the New Zealand permanent residents that were able to join the Australian Defense Force from 1 July of this year, and already we see nearly 400 New Zealand permanent residents in the pipeline with applications to join our Defence Force right now. And for all these permanent residents from the Five Eyes nations, once they join our Australian Defence Force, they will then be expected to take out Australian citizenship, when they become eligible after three months of service."