Quite how telling the Russian government that the Americans will respond in kind is tantamount to a declaration of war is beyond me. By that logic, and the full response from Obama as per his press conference, we could only conclude that it is Putin who has declared hostilities.
But, let's face...
I think it was less to do with Obama and more with the establishment candidate. Contrary to popular view, many Obama voters switched to Trump. I think the issue was with Clinton.