Surprised no one has mentioned our "illustrious" National Athem, The Star-Spangled Banner in this discussion. Francis Scott Key wrote the lyric while watching the British shelling of Ft. McHenry in Baltimore Harbor during this war (Sept.13-14, 1814). And, consequently, the US wound up with The Star-Spangled (usually mangled) Banner as our National Anthem instead of America (the Beautiful). For that alone you could say we lost the war!
But, of course, all through school we were taught we won the War of 1812 simply because we staved the British off from attempting to conquer and take back our young nation. But they also taught us that Lincoln freed the slaves and everybody lived happily ever after...(Reconstruction? Jim Crow? Sharecropping? What's all that?)

One war they never taught us except for a mere mention was the Mexican - American War (1846-48). I always wondered why they didn't (because it was a mighty sizeable conflict) until I discovered that Gen. Winfield Scott, violating centuries of wartime "etiquette," ordered the shelling of Veracruz and its civilian population. Wouldn't want schoolchildren to think that we Americans were responsible for relaunching ancient (and, now, modern) barbarism back into warfare, now would we?

Note: The they referred to is "my teachers," of course. Obviously, as already noted on this board, lesson plans vary tremendously for a variety of reasons!