WASHINGTON — Education Secretary Linda McMahon is sending a letter to 43 million Americans with student loans — about 9 million of whom are in default — to notify them that the Treasury Department is taking over debt collection, The Post has learned. The letter describes the transfer of responsibilities as a way to protect taxpayers by improving the efficiency of the collection process — after loan repayments were paused through much of the Biden administration, with borrowers protected from delinquency through September 2024. “For too long, Americans have shouldered the consequences of poor leadership and persistent mismanagement of our...