America set up England in the Revolutionary War, a few drunk farmers went to Concord, Sam Adams fired his pistol and the Brits started shooting, starting the Revolution. War of 1812, An American plot to steal Canada that backfired and we had our capital burned. (Cost cutting by Jefferson reduced the military). Civil war, Lincoln, forced Rebels to open fire on Fort Sumter by supplying the fort to lock up one of the few seagoing ports in the CSA. WW I started when Wilson had England send the Lusitania (Traveling slow—in sub infested waters) full of rich Americans—to be sunk! WW II FDR, prods Japan to attack and moved the fleet to Hawaii (making sure the carriers were at sea). A case could be made for US using such tactics to get into wars. But, wars are started for more than one cause.
So what other causes were involved in President "Manifest Destiny" Polk's declaration of war against Mexico?