As US allies reel from Donald Trump’s weekend comments encouraging Russia to attack European allies if they don’t meet NATO budget contribution goals, multiple former Trump advisers warn in my upcoming book that the former president will seek to formally withdraw the US from the NATO alliance if he wins a second term.
In order to do that Trump would need a MAGA-Republican majority in the US Senate as well, due to a recently bi-partisan enacted law by Congress stating as much - https://thehill.com/homenews/4360407-congress-approves-bill-barring-president-withdrawing-nato/