Maybe. What would we have done, though? Tested everyone, even those without symptoms?

If your symptoms are mild enough to not need hospitalization, your instructions are the same regardless of if it's the coronavirus, flu, or common cold. Now they're just telling the general population to follow those instructions.

What really disappoints me is that people seem to think it's okay to ignore those instructions if it's not the coronavirus. One possible silver lining to this mess is that flu cases will probably be significantly reduced in the short term.

Actively tracing contacts and testing them would be the key thing. When one person is found to be infected, you figure out where they've been and who they've interacted with, so you can test those people. Any of those people test positive? They go into quarantine and you trace their contacts. That's how you slow and eventually break the spread. Note that contacts don't need to be symptomatic to be tested.

Instead we're effectively doing the opposite, which is testing IF AND ONLY IF you BOTH have symptoms AND can prove contact with a confirmed case. Which doesn't do much to stop transmission (it's too late at this point; you've already spread it), and certainly doesn't give an accurate picture of the prevalence or behavior of the disease.

Have any nations found success with that strategy? Could it be that we simply couldn't conduct that level of investigation fast enough at scale to be effective? And are the tests accurate enough for that approach to work?

It's my understanding that this is what South Korea, Hong Kong, and possibly Taiwan did (and are still doing). As well as China once they acknowledged the outbreak. (Which is not to condone China's methods of enforcing the quarantine.)

(EDIT: Found an article I saw the other day about this being done in an Italian town with the claim that the virus has been "eradicated" there as a consequence: https://www.theguardian.com/commentisfree/2020/mar/20/eradic...)

I'm just a lay observer of all this, not an authority. But my impression is that the U.S. could have done it effectively if a) the CDC test situation had not been borked and b) the federal govt had acknowledged the risk of epidemic (because I expect it's the CDC who has expertise in this tracing exercise, much more than state health departments).

As to whether it's too late, I honestly don't know. But it seems like it would be useful in controlling the epidemic regardless of its state.

The horse left that barn when we had a couple weeks of unknown spread in Washington state.

Yes, although it is possible to put the horse back in the barn with lockdown measures. And then IFF you have the extensive testing, those measures can be relaxed after a few weeks without cases exploding again.