US entered the conflict in Iraq and the reasons that the US entered the conflicts as described in the Domino Theory. How are they different? How are they the same?

Domino theory was based on falling Domino, according to which the political events of one country affect the political events of the neighboring countries. So, we against Vietnam was influenced b this theory Due to this, Soth East Asian Treaty Organisation was made, in which alliances were made which were in favor of Iraq, in the Iran-Iraq war. But, this actually caused reverse domino effect due to which liberalism occurred. And the war in Iraq was entitled as No Domino.