How different do you think things would be in John McCain won the presidency?

Trump wouldn't be president.

A Neo-Conservative, McCain would have the US mired in even more Mid East quagmires. John Mcain was a hero and heroes believe they can save the world, despite History proving otherwise.

Well, it would be many years ago, that's for sure. Also Nickelback would still suck, but that's not what you asked.

McCain was an intelligent guy, especially compared to Dubya, but he was a hardcore moderate. That's why he lost, in fact. He was still a politician, which means not to be trusted in any way, but he was too down to earth to win a presidential election.

If McCain had run to be the leader of a more boring country, like (just for example) the UK or Canada, he would have won in a landslide. But that's because Canada and the UK are very right-down-the-middle countries, which the Americans view as boring and uninspired. Americans don't want pragmatism, they want excitement. That attitude has, for the most part, served them very well throughout their history. Not all the time, but most of the time.

Envasion of Syria.

McCain would have been like W Bush. He was a squishy moderate that liked to run to the press to tell them how bad the Republicans were. He craved accolades from the media for being a "maverick" but IMO, that just made him lack real principles regarding political issues. It would likely have been the same old thing. Republican establishment gave us the worst Republican to run with McCain and gave us Romney, the creator of Obamacare to run against Obama. I think McCain would have likely created a need for an outsider like Trump to reform Washington and drain the swamp, just as Obama did.

If McCain had won the Nomination in 2000 then Gore would have been President. But no matter who won that election Gore or McCain I think there is a good chance 9/11 would not have happened simply because that group hated the Bushes so much. They would have had the same plans, but may have been discovered. And there is a 100% chance there would have been no Iraq invasion even if 9/11 had happened, providing a very good chance that we could have actually fixed Afghanistan. If McCain had won in 2008, with Sarah Palin on the ticket we would have been in batshit-crazy GOP-land 8 years sooner, and Hillary would have won in 2012 and be into her 2nd term

If McCain had been elected in 2008 instead of Obama, I doubt Trump would be president today.

McCain is a moderate. A moderate cannot be President because no moderate will be selected during the primaries. It is an oxymoron. To win the primary you must be, at least, a party moderate.