That's quite an overreaction. If you kill a British cop while trying to smuggle guns or drugs into Northern Ireland, I would hope that Britain wouldn't declare war on the US.
Nice of you to protect us here from extreme conjectures, but you underestimate the events IMO.
Not JAII (just another isolated incident); these events are state-sponsored with the known complicity the beligerent state of Mexico openly assisting and promoting such activities to open the border. The drug running alone is assisted by Federales on the Mexican side. The govt collects the bribes too.
Further if you look at Squantos posting #37 - you see signs of national security at stake as well.