I don't think it's so much what we've done but what we're ready to do....
The 24 bombers moved to Guam is something, but those stelth fighters in Seoul will be obliterated in the event of a full-scale conventional (nuclear aside) attack by North Korea. If and when the war comes, there won't be a building standing in Seoul within 24 hours. North Korea's artillery and missile attacks will make sure of that. That's why South Korea isn't going to support any US plan to invade North Korea. The bombers we have in Guam can provide some cover for the South Korean military, but that's about all they can really do. The terrain where North Korea has most of its weapons dug in isn't really feasible to bomb. If we want to take care of the North Korean problem, it's going to take lots and lots of US forces on the ground, and a full commitment of US military power and weaponry. We were in great shape to do that before Iraq, but I don't know that we have the manpower or weaponry to do anything about North Korea any time soon - short of a full-scale nuclear attack, which we all know isn't going to happen.