Automakers are grappling with a changing market. The Trump administration hasn't made it easier.

Motown's glitziest annual tradition kicked off Sunday night as Cadillac, one of the most venerable brands in the business, took the cover off of its newest vehicle: A three-row, luxury SUV it calls the XT6. Rolling out to a cheery soundtrack, fog and roving spotlights, the XT6 debuted with a flourish as Cadillac introduced it as "a vehicle that offers…