SAN FRANCISCO — As senior Trump administration officials say they want to amp up cyberattacks against China and other geopolitical rivals, some government veterans warn that such an approach would set the United States up for retaliation that it is increasingly unprepared to counter.Alexei Bulazel, senior director for cyber at the National Security Council, said earlier this month that he wanted to fight back against China’s aggressive pre-positioning of hacking capabilities within U.S. critical...