Are you suggesting hunting enemies in countries like Russia/China is going to go down well?

How would you feel if they decided to declare some enemies on US soil and start hunting them on your patch?

Unless your assumption is that Russia/China would agree to the hunting of course, but that does seem unlikely.

Why not? $40 trillion dollars in weapons spending would easily save $10 billion dollars it would cost to hire security professionals on an annual salary to patch software and ensure that intrusion was more difficult.

This is exactly what they're doing now, they're just doing it with law enforcement agencies and not military. Military is honestly going to be worse at all of this, as they don't have the investigative capacity. This also ducks the very thorny political problems where Ukraine (never mind Russia!)are NOT going to allow US military involvement in domestic affairs, but do have agreements with Interpol that make this possible. Nobody wants extrajudicial military extraction squads acting on their turf.

I'm sure the various 3 letter agencies (NSA, CIA, etc) are already involved to a degree that's not publicly known.

Military is a pretty blunt instrument, also, the US government is not the only government that has military and "more covert methods".