We never had that chance because you cannot coordinate 8 million people, much less 8 billion. And nobody was going to shut down all the coordination points of society such as grocery stores, pharmacies, and hospitals.

The CDC knew this at the time. The "flatten the curve" message was "slow things down enough until we know more and can avoid our hospitals from being overwhelmed and more people dying."

True. Even in the strictest US states, the lockdowns were actually voluntary stay-at-home orders, because very few people could survive more than a few days without trips to get food, and there are a lot of necessary services that have to happen. Just for one small example, how many homes across the country need a plumber in a typical day, and would have sewage problems and disease eventually if plumbers weren't allowed to move around to do their work?

The idea that the virus ever could have been stopped if we'd just all cooperated harder was a retcon invented later by people who wanted to criticize other people for not caring as much as they did. The actual experts always said the best we could do was spread it out.

Australia managed to keep COVID out for nearly two years, before they ran out of resources. Stop all non-local travel, identify where it's spread to, establish a buffer zone, wait to see if we drew our buffer zone large enough… two weeks later, and most of the world can be business as usual (minus globe-hopping); two months later, and COVID-19 is as dead as smallpox… assuming everything went right. Realistically, it might take four or five months for everyone infected to recover (or die): but it's a lot easier to enforce a quarantine when there are a hundred cases in the whole world.

This would be expensive, but as expensive as what we did was? Surely not! So, other regions providing funding and resources to the regions taking on the burden would be a strictly rational move.

You might say "oh, but people didn't know about the spread!"… but that's a ridiculous claim. The Less Wrong crowd tracked it in near-real-time from open source intelligence, and governments had access to more intelligence than that. The number of governments giving nonsensical advice, like "masks don't work because the respiratory disease is not spread via aerosols", and "replace your soap with dilute alcohol", lampshades a broad coordination problem. (We're not much past the "sweet-smelling herbs will protect from the plague" advice of yore, it seems.)

The things we needed to do were done – but for ridiculous political reasons, nearly everyone waited until after the disease had reached their regions to close their borders: internationally and intranationally, at every level! (The algorithm in Pandemic II's easy mode was more sensible than that.) So much of that effort, that psychological torment, was wasted. Even if the whole world had taken Australia's approach, we still would've brought the disease to manageable levels within a year. But there wasn't the political will… and so it goes. I think we're less prepared for the next novel disease outbreak, now.

New Zealand had about 5 million people, and PM Ardern successfully implemented a total lockdown that drove new COVID cases to effectively zero. Then she was voted out, and per Aurynn Shaw the plague ships were let back in.

It can be done. It just requires leadership, discipline, and the willingness to take strict, decisive, politically unpopular measures against violators and spreaders of misinformation. As Schwarzenegger said, when there's a pandemic on, screw your freedoms.