How, precisely, does one extrapolate from the EU (of all places) to a one world government? The variation across the world in everything from cultural and religious norms to even technical approaches to solving problems is extreme, and it has been like this since forever. The genesis of the EU seems, in my view, an evolution of American dominance of the continent after WWII. Is that what you mean? Further American influence tends to encourage (or coerce) countries into further integration?
I’d put the odds of any of that happening on a global scale at approximately zero, because there actually have been globe spanning empires in the past (multiple iterations, in point of fact), and they all collapsed or shed their empires when it became clear ruling it was no longer in the interest of the Sovereign or the Subjects.