The Trump White House has repeatedly sounded an alarm about visitors with ties to China’s Communist Party coming to the United States, arguing that they are a potential security threat. But the administration appears to have literally left the door open to a member of a Chinese government group when it went along with a plan to give the biggest purchasers of President Trump’s digital currency access to the president and the White House. Mr. Trump launched a so-called memecoin, a type of cryptocurrency, just days before his inauguration. To bolster sales, the president’s business partners created a contest in...