"Remember the Alamo" was a rallying cry for Texan revolutionaries, most of whom were immigrants from the United States, calling others to avenge and honor those who died at the Alamo Mission. It fits into a long American tradition (not unique to the US of course). "Remember Fort Mims" became the battle cry for the United States during the Creek War. "Remember the Maine" was the sales-pitch for the Spanish-American War. "Remember Pearl Harbor" / "Remember Dec. 7th" were both used by Americans during WWII. "Never Forget" in association with the terrorist attacks on Sept. 11th, 2001 is a variation on the genre.