If the Apollo 11 crew were stranded on the surface of the Moon.
...They'd have perished there 43 years ago.
That is true.
I have no doubt that NASA would have resolved whatever caused the accident. There would almost certainly have been at least on more test flight of the LM and then another landing attempt made. The USA would have still been the first to the moon albeit missing JFKs target of the end of the decade.