Regarding Leviathan being analogous to a tsunami:
It would’ve been quite appropriate if he’d sunk Honshu rather than Kyushu, or if the Fukushima disaster (which happened in March 2011, so before Worm even started but still topical by the time Leviathan was introduced) had taken place on Kyushu instead.
Honshu is quite a bit bigger and more populous than Kyushu and Newfoundland, though, so it’d paint his powers as even stronger than they already are. Maybe Kyushu was indeed mentioned because Wildbow wanted to reference the Fukushima disaster but found that Honshu was too big and important, and so went for a different island while still getting the reference through by hitting Japan.
But then again, even if he wasn’t specifically referencing that disaster, Japan is well known as a frequent target of tsunamis. Hell, it’s where we got the word from. So even without Fukushima, Japan as a target of the tsunami Endbringer is super appropriate.
I wonder if Hawaii and/or Iceland have been struck by Behemoth and New Orleans by the Simurgh.