maybe sorta, but most likely just Trump talking. The coast guard already spends a ton of time going after narco subs and use Navy assets for some of the surveillance heavy lifting, so using the military to do interdiction at sea would just be them using more Navy assets to do what the Coast Guard is already doing. I don't see boots on the ground in Mexico being a thing without Mexican assistance. The logistics of it is just fucking impossible. You're not sending 8 guys after CJNG like in a movie. Could they in theory do really quick deployments over the border to hit something really close with a really small force and then come back...maybe, but even that seems pretty fucked up.
I could see them hitting targets with missiles, but the Mexicans (and the world) would see that. The most likely would be small special forces operations to take out specific targets, but that's a hilarious waste of time. These organizations are so decentralized now. You could pop the head of a different grupo every week and it wouldn't change anything about how the organization works or it's effectiveness. The cartel names are mostly branding now. They're all made up of loosely aligned armed groups that operate more or less independently. Sinaloa cartel has been at war with itself for well over a year now. The 2 biggest armed groups of the Gulf Cartel have been at war with each other over control of Matamoros and Reynosa for like 15 years now. The cartels just don't exist in the way north american journalists and politicians think that they do.