Sure.
But not all you can see you can hit.
Also theese things are stationed some 100 km inside Russian terrtitory, with range of 400 km (lets say 200 miles) it is hard to get them in range of your onboard missiles. Also S-300/400 are protected by Tor or Tunguska systems.
And that is if you get to see lounchers.
And if you are left with usable satelites to see them at first place.
Cypruss is using S-300 missiles to defend against Turkey.
No one is going to attack inside russia. If the US did it would be with ICBM's and SLBM's because we know they would retaliate with nukes.
Like a said yes they are dangerous but totally defeatable if we need to do it.
Not based in Cyprus. After all the uproar about basing them in Cyprus they are operated by Greece in Crete.