Former president Donald Trump went on a tirade about commander-in-chief rival Joe Biden, claiming the sitting president is “humiliating our country on the world stage.” During a speaking event in Racine, Wisconsin, the embattled GOP frontrunner addressed recent clips of Biden casting doubt on his cognitive abilities before making his own gaffe. “You saw what happened this weekend. It’s turning the United States into a total joke all over the world. First, he wandered off the G7 in Europe on this stage. He looked like he didn’t know where the hell he was, but he didn’t know where he was,” Trump…