The issue is respecting the sovereignty of Mexico. Trump has stated his intentions of couping Sheinbaum, as well as his desire to colonize Mexico and annex it into the empire. Drug gangs are a domestic problem for Mexico, which should be handled internally (and are). Trump wants to use them as pretext to invade to achieve the goals he has previously stated but under the guise of opposing cartels. Not to mention that the war on drugs is what created and sustains those groups but I digress