The American said his media commitments had become an "issue" at Wimbledon.
"When the US Open starts on Monday, he's got his people. I'm pulling for him and want him to do well," McEnroe told reporters.
"I'd love to see all the guys play their best because I think it's better for tennis. But it's best to sort of separate at this stage. It will just make life easier for everyone."
Raonic, who also has former world number one Carlos Moya among his coaching ranks, will begin his U.S. Open campaign against Germany's Dustin Brown.
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(Reporting by Nivedita Shankar in Bengaluru; editing by Amlan Chakraborty)
