By far the biggest one is testing, testing, and more testing - instead of not wanting the numbers to go up because he thought it would make him look bad.

If we had proper testing early on (something other countries managed to not fail at), we could have identified and isolated the spread. Localized shutdowns to slow the spread instead of needing to lock down nationwide would have been much kinder to the economy.

Obviously work could have been done to evaluate PPE, ventilator, etc. levels and arrangements made to stock up.

There could/should have been planning for actions to take in certain scenarios. Examples would be to enact Plan X when we have cases in 5 states, or enact Plan Y when we have the first case of community spread, etc. I'm assuming those sorts of plans exist in the pandemic playbook work done by the government over the years - would obviously need to be updated/tweaked for COVID-19, but it's not like they'd be starting from scratch. Instead of supporting planning, the President was wishing it would miraculously disappear.

I get frustrated by the argument that it's all 20/20 hindsight and no one else would have done it differently. I started reading what experts were saying around mid-February and they were screaming about things like testing that needed to be happening while the administration was instead blowing the whole thing off, and they were predicting what that would mean. Their predictions were right. I'm glad I followed what they were saying because I used that information to prepare for self isolation - and I struggle with the idea that I, some random citizen, could listen to experts and prepare but our government couldn't be bothered to do the same.

Again, we absolutely would still have problems even if Mr. Perfect Fictional President had done everything perfectly. We would still have a lot of deaths and a crippled economy - it's a pandemic, that's what they do...but for a problem that literally grows exponentially, completely dismissing that problem for 3-6 weeks by definition makes it significantly worse.