There's already branches of cabinet-level departments that try to do this. In my opinion they're having about the same level of efficacy as one might expect in any other set of large-scale changes in very large old companies with a wide variety of internal systems and needs. If you look you'll find a plethora of government-led attempts to secure various critical industries.

You'll also note that entertainment companies and hospitals are routinely breached. There's perhaps room to question if they are indeed practicing good cybersecurity.