re: Bunker buster technology
A bunker buster like the GBU-28 that was used in Afghanistan penetrates about 7-8 meters into the ground before exploding; good for hitting bunkers but slightly short of penetrating a several Km deep ice covered satellite. Even nuclear buster bunkers are not that much more penetrating- from a strategic point why would they be? They are also very heavy and flying one to Europa is a pretty inefficient way to spend money... although it would be kind of fun to watch it go off.
For more info on Bunker busters see "How stuff works-bunker busters"
http://science.howstuffworks.com/framed.htm?parent=bunker-buster.htm&url=http://www.cnn.com/2002/US/11/18/hln.terror.us.air.force/