The US and Europe could have done this. England could have done this. They chose not to and exchanged a month of pain for a year of pain and 100s of thousands of deaths.
Germany is more locked-down internally (like Australia and NZ) than it is on its outside borders.
Is it a mess? Yes. Should it be done better? Yes.
But honestly, if Germany was an Island, it would be doing just as good as Australia and NZ. It locked down internal travel several times, had one of the best contact tracing when it was still possible, and generally just got outplayed by new strains swamping through land borders that neither NZ nor Australia even have.
No, absent martial law being imposed by the feds, this was never an option. The US federal government is not legally able to do the same things that unitary nations like South Korea and Australia can do on a whim. States delegated certain limited powers to the feds at inception, and reserve many, while affirmatively proscribing the federal government from doing specific things. States in the US are not simply local administrative bodies, they are essentially mini-nations that have out-sourced certain shared services. I’m speaking generally of course but that’s a better way to understand civics in the US vs some other (most?) countries. As a consequence of this system, states bear a lot of responsibility for their own policies. What do you think the tolerance would have been (or still is) for Joe Biden, much less Trump, declaring martial law? About zero, I’d suspect.
The right to travel within the US, like free speech, is near absolute. The due process hurdles to temporarily remove that right from an individual are very high; you can't do it with an edict nor de facto travel restrictions by abusing regulatory power (which has also been tested in the US Supreme Court).
Australia has significantly weaker individual freedoms than the US. This is one of those cases where those differences become apparent. Everyone asserting that the US should restrict travel like everyone else is ignoring that it is expressly illegal for the government to mandate such at thing in the US. No one in the US government is interested in dealing with the backlash such an attempt would elicit.
This appears to be wrong: https://www.justsecurity.org/69770/can-governors-close-their...
A thorough reading of that case law makes it plain that the proposals with respect to COVID would never pass judicial muster. In fact, there is considerable case law where attempts at such prohibitions were rejected outright but little curiosity in the above link as to the conditions and circumstances that caused the courts to throw them out.
The government knows that the courts won't allow them to cherrypick and selectively quote case law. It isn't an accident that every State in the US, across the entire political spectrum, came to the same policy conclusion regarding freedom of travel.
This guy from Yale thinks the same as the first one I linked:
https://www.bloomberg.com/opinion/articles/2020-03-18/in-a-p...