They have historically said aluminum in Canada too…
It’s not an American term. It’s literally what the British discoverer of the metal named it (after originally naming it Alumium), both because it resembled platinum as well as wanting to associate it with the more prestigious metal.
Aluminium is actually the “incorrect” way of spelling it anyway because it comes from the second neuter declination from Latin where -um is the correct way. Which is why you have plumbum (lead, Pb), argentum (silver, Ag), aurum (gold, Au), ferrum (iron, Fe), hydrargyrum (mercury, Hg), copper (cuprum, Cu), stannum (tin, Sn), molybdenum, lanthanum, and tantalum. Arsenic was originally arsenicum as well.
The second neuter declension from Greek is where you get -on elements like the noble gasses. Neon, krypton, argon, xenon, radon. And then helium, which by its Greek etymology should be helion instead of helium. Also Silicon, carbon, boron, and oganesson.
Oganesson by the IUPAC rules should actually be Oganessium, because the naming rules required all new elements to end in -ium regardless of properties. They ended up naming it oganesson because it falls in the noble gas group, even though it’s predicted to be a metallic solid at room temp and not a gas at all.
