It takes time but a mess like this can be corrected. You first isolate/segment,then you determine scope and source of the compromise/failure as well as external communication channels. The cleaning up part starts when you first disable the communication channels, get forensics imaging as needed,surgically remove threats on critical systems and slowly rebuild systems that are less than critical.
Think of america as a network instead of a system, the hackers have seized control of the domain controller and other critical systems but they haven't compromised all systems or prevented admins from kicking them out.
The problem is not actually fixing America but convincing anyone how deep and widespread the problem is. You can fix it but the bad guys will just get back in, it's not just a cleanup but a systemic change on how security(national security,public security,etc..)is done. In american politics we're talking about changes to the constitution, perhaps even a rewrite. You can convince people a new president that will magically fix things is needed but you can't convince them the very foundation of the country has been cracked due to changes that happened over time and will cause a structural collapse.
There's a Churchill quote that's similar. Something like: The problem isn't winning the war, it's convincing others that it needs to be fought.
What's worse, it's not really like you're a consultant, because then you might be able to leave it behind. It's more like you all work for that company, and it's a revolving set of promotions and demotions, and you're forced to watch people abandon your work for some other goal that you think is at best less important, but have no real ability to influence.