I fail to grasp the sentence though. What's a thalassocracy supposed to be in today's world?

There's a similar train of thought that sea-based empires defeat land-based empires when the two do battle and some people view the conflict between the USSR and the United States during the cold war through that lense.

I take their overall point there to draw a parallel to small states as islands, small spits of sand, connected by the thalassocracies, or oceans, of the US and USSR. In some sense, this is actually reality, especially under the US system of global economic hegemony via free trade (or some approximate, thereof).

Not an LLM but maybe a francophone or a logophile.

The two organizational principles are so fundamentally different, they're almost apples and oranges.