Cruz should avoid getting photographed driving a tank, wearing any funny looking hats, or shaking hands with any neo-Nazis while he’s over there.
FDR shook hands with Stalin and called him Uncle Joe. He seemed to do all right. Nixon shook hands with Mao and had China's UN seat given to Communist China in order to peel it away from Communist Russia. Nixon suffered no negative political consequences from this. That's probably because unlike Stalin and Mao, Ukraine's neo-Nazis aren't actually responsible for the deaths of tens of millions.