My son was born with a high respiratory rate. Is there a correlation with croup or any other respiratory illness?

Unclear. I am unsure how old your son is now but if the fast breathing was only in the first few hours after being born and has then been well it is unlikely to be connected.
Transient tachypnea. Many newborns demonstrate a transient period of rapid respiration as they clear some of the initial fluid from their lungs. Prior to birth, infant lungs are much like a sponge that has never been wet, compressed with lung fluid from its time developing. The initial minutes after birth promotes an absorption of that fluid into the blood, so air can pass easily. It is not predictive of lung weakness.