Australia has passed a law which apparently requires tech workers to develop backdoors which can defeat a company's encryption and security features, without informing their employer, if ordered to do so (and it is now a crime if they refuse, or inform their employer about what they have done). As far as I can tell, this Australian law applies to Australians living abroad. (Much of the broad language may also apply to non-Australians living outside Australia, but the jurisdictional claim seems a little weaker there).
The US, and other countries, have laws prohibiting discrimination in hiring based on national origin, with some exceptions.
Can a US employer discriminate against (refuse to hire) Australians as a step toward protecting their company and products from having the Australian government force in a secret backdoor?
Update, originally intended but made more explicit following comment from @paulj: Please be sure to include consideration of individuals who are both Australian and US citizens, if that is permitted.