It’s useful in the argument that (1) states, as they’ve grown in size have also been reigned-in due to the power that comes with their size, and (2) that companies, as they grow in size, must be reigned-in due to the power that comes with their size (anti-trust, anti-monopoly).

Metaphors are useful but they can also just confuse the issue through unnecessary abstraction. The fundamental question is already there at the surface: it’s not about market capitalization or about gdp, but about the power that size in either metric represents. That’s the characteristic binding these two dissimilar ideas together.