In what way was the tet offensive a strategic blow

It was a strategic blow because it destroyed the army's morale and the public support for the effort. Up until it, there was a public consensus that the North Army was weak and that the US was winning with a landslide, but the Tet offensive showed that the opposite is true and that the US army is not unbeatable, even though it was highly technologically advanced and the North was heavily underdeveloped.