No they can't trace an individual having a bitcoin or holding of any crypto. But the government can impose some fee on the transaction like additional fee when you go to an exchange. It is really possible like here in the Philippines that the exchange like coins.ph have been regulated by the government agency and the Bangko Sentral ng Pilipinas that gives coins.ph a license to operate. In this way coins.ph could be directed to get an additional fee for the government fundings in every exchange or transactions to be done.