Bastogne (or the Battle of the Bulge) and Khe Sanh were more than just defensive actions, they were favorable opportunities to engage the enemy. Hitler foolishly ventured out from behind the West Wall where his last reserves could be degraded in the least costly (to the Allies) manner. This article doesn’t mention casualties, but Khe Sanh was very costly to the enemy.
You can even argue that the assumed ability of U.S. bases to resist any attack is counter-productive as what we want is for insurgents, in Afghanistan or Iraq, to gather in an attack like Khe Sanh. Perceived vulnerability encourages the enemy to attack and attacks against well-defended positions have been disastrously costly since the American Civil War.