To be fair, he didn’t take the side of Putin over America, just the American investigator. As evidenced by this very thread and many comments on this board, there are quite a few Americans who are with Trump on this.
You mean he took Putins word over that of the conclusions of all our intelligence agencies, Congress and even people in his own administration (Dan Coats, Pompeo, etc..)
Also, Mueller delivers indictments on 12 Russians and provides detailed information on exactly what they did, how they did it etc.
Trump ignored all that and took the word of a former KGB agent over his own country
So yes, Trump took the side of Putin/Russia over America
Keep in mind he walked that back yesterday and then walked back his walk back today