It shouldn't be very hard to strap a radar detector/seeker in the nose of these,
It is not that easy- just ask the Iranians with their attempts at jury rigging much simpler 1970s systems.
You would have to considerably modify current US cruise missiles – everything from flight surfaces, internal composition (weight endurance), possibly power plant if the seeker adds weight etc etc.
Also most US cruise missiles are subsonic whereas the Russian AD systems are supersonic with speeds up to Mach 8.5.
Makes the cruise missile a really poor choice for slugging it out with AD systems.
The whole Russian system is actually designed to take out cruise missiles – S300/400 at long range, Buk/Tor at medium/short range and Pantsir for point defence. All coupled with huge amounts of radars and comms devices. Given you're talking Russian or Chinese mainland, this includes extremely powerful radars that can detect (but not necessarily target) stealth aircraft.
This is the cornerstone of A2/AD.
Our friends, the Israelis, have a much better longer range anti-AD system in the form of the LORA quasi anti-ballistic missile system.
This weapon system's flight profile means it completely avoids the air defence systems. Due to its angle of attack, Russian and incidentally American Patriot and other western radars cannot track it.
And the missile's target point can be adjusted.
The other Israeli development is the Delilah – a combination of cruise missile and loitering ammunition. It's small and actually quite slow so not as easily detectable.
The main disadvantage of these two systems is range – 400 km for LORA, 250 km for Delilah (Delilah requires aircraft to get within range of enemy SAMs*). This is fine for ground combat in close environments like Israel-Syria or Nagorno Karabakh but not so useful in a Pacific context where approaches to land based SAMs are going to be defended by coastal and sea based long range anti-shipping missiles, aircraft and submarines.
Again this is the whole point of A2/AD – multi-layered defence.
*Israel has one massive advantage in neutralising Syrians air defences – close proximity. Thus Israeli aircraft can launch weapons from within Israeli airspace! The Syrians don't target Israeli aircraft within Israeli airspace for obvious reasons.
Problem is west has been very slow in acquiring loitering munitions or hyper sonic quasi ballistic missiles. The emphasis in the west is still on short range tactical fighters to for strike capability ie F-15E, F-16C/V, F/A-18E/F and of course F-35 as well as older forms of cruise missiles. Even the F-35 is vulnerable in these environments as it needs support from non-stealthy tankers based on commercial airliners!
and they can hit GPS coordinates provided by drones, if the drones don't take them out first.
As mentioned the existing US cruise missiles are relatively slow and need to be deployed from out of range of defences – this could would give the Russians/Chinese time to detect strikes and redeploy as well as ramp up countermeasures.
The drones would have to be long range types that can deploy well out of the range of aforementioned defences.
I suspect such things are in development. I'm actually surprised that the new B-21 stealth bomber hasn't been earmarked as a deployment tool for large swarms of drones.
One can imagine B-21s "seeding" key areas with swarms of autonomous drones which then go around blowing up anything with the right kind of electronic signature or visual profile (still science fiction but work is progressing on this).
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Oh and Japanese constitution still prohibits certain offensive weapons.
It's why their new light carriers are classed as destroyers.
However they are working on a new series of hypersonic cruise missiles mainly for anti-shipping but a land attack version has been mentioned. The program's status is unclear – SDF procurement programs are often scrapped before they come to fruition on grounds of excessive cost.
conflict in the world requires American attention. 
