Not to mention that testing is now another moving target. It appears that antigen rapid tests may not even detect Omicron until a couple days past your point of infectiousness, so the the messaging even if we could figure it out correctly is getting to be more complicated than much of the public is going to have the patience to parse.
The problem is structural though. Public health in the US has never been located in the Federal gov - it's largely a state and even county responsibility in most places. And then you have GOP govs and legislatures hamstringing their own public health depts that are trying to respond. For the fed to build out something like a massive testing capability they have to start at ground zero. Simply paying for tests, as they have been doing so far, doesn't really control the supply as we have seen the manufacturers pull back when they anticipated demand would fall. To do it right you really need a package of enabling legislation to set up some new capacities, but what are the odds of anything getting done legislatively?
What maybe they could have done, and probably should have, is set up a standing federal governor's conference where they could have tried to get coordinate to keep state govs on the same page - but again, what would that have looked like when most of the GOP govs refused to show up?