American is an element that sits (in the periodic table) under Europium and thus names after America. I expect element 149 would be named Australiacisium, but that’s just speculation. It’s used in Smoke Detectors and in some nuclear battery applications. It’s tied to Bald Eagle for obvious reasons.
Marie and Pierre Curie were long term researchers of radioactive isotopes and Curium was named in their honor. It’s a hard and dense metal that forms strongly fluorescent bonds with organic compounds. It’s from this ability that some have got the idea of people glowing after exposure to radioactive isotopes. Curium is mostly used to produce other radioactive isotopes.
Crystal Jellyfish are round relatively small Jellyfish that can survive rather depleted oxygen regions. They can be bioluminescent and thus this is why they are tied to Curium.