The fact that we move around a lot between states is why it was stupid to leave covid things to the states to sort out to begin with. It wasn't about WHO made that decision (indecision, really), but that it was stupid.
It's a feature, or a bug, depending on your perspective, of our federal system. We leave most police powers and most emergency powers to the states.
I'm not sure that many of the actions that you would want the federal government to take would be found Constitutional. There are instances where the federal government can assist, but often it requires the states to request their assistance, it cannot be forced.
Now, you may claim that a well-crafted response at the federal level, if the federal government HAD the powers you seek, would have made our response to COVID better. Maybe that's true; maybe it's not--after all, I'm not sure the person in charge of the executive branch last spring would have led a well-crafted response
and I think you'd agree. But most of us who are in favor of the federal system we have would argue that giving that much power to the federal government would have a lot of other negative consequences in other areas, and possibly even with 500K dead from COVID, wouldn't be worth it.
If government is benevolent and intelligent and possesses perfect information about everything, it's a wonderful thing to centralize everything. That would be utopia. But government is led by people, and people are neither universally benevolent nor intelligent nor possess perfect information. So we avoid centralizing everything, because that would be Soviet Russia or modern China.
