A closer parallel would be Korea. Did we pull out in 1953? How much has it cost to provide a shield over South Korea and Japan (and Taiwan)for fifty-six years? The flaw in Nixon's plan was not leaving a trip-wire force along the 17th Parallel as we did along the 38th parallel in Korea and in West Berlin in Germany, as a guarantor of good faith.
Had Nixon done that, the North surely would have set that trip wire betting that America did not possess the resolve to send hundreds of thousands of troops back into Southeast Asia after withdrawing them. And if that happened, what signal would that send to our enemies regarding the Peninsula and Western Europe?