Ali's drafting had an interesting and little know side effect, the USG changed its minds about letting the Apollo astronauts do Vietnam tours. as many had asked during the hiatus after the Apollo 1 fire. Previously they had been worried about the optics of what would happen if the NVA shot down and captured as Astronaut. The overwhelmingly positive response to Ali's service led the, to change their minds. That means Gene Cernan does not get shot down and win the MOH for his courage in captivity and legendary escape in 1971. He does not enter politics and become POTUS in 1988. On the flip side, he does have a chance to walk on the moon*. ALthough if he walks on the moon, he does not fly Apollo Soyuz in 75; which kickstarted his political career, and he got it cause he was a war hero and it gave the mission a lot of publicity.
*Contrary to what has been reported, he never was a realistic candidate for being the first man on the moon instead of David Scott in 1971, he had only one flight before his captivity, and a non Command one at that, Scott had two priors. Cernan would have probably gotten either an early Lunar orbit mission as CMP/LMP and a later landing mission as CDR.
OOC: This is not totally dreamt up. The active duty and ANG/reserve astronauts had to maintain proficiency in the Apollo era and during the 20-month break after Apollo 1, several, including Cernan, did ask about going to the 'Nam. They were turned down, and told that they were needed more for the Lunar shots; but also because the USG was worried about them being captured or killed and the propaganda value for the Government in Hanoi. I have given the 1971 date for a landing (in OTL, Scott's Apollo 15 flight took place in July that year) since the loss of experienced astronauts would push back the schedule, the early Apollo lunar missions, typically contained either two or for '10, '11, three veterans, the did not want rookies on early lunar flights.