Actually, I''d say the opposite, in that in the last 100 years we've trending towards a much more fragmented world of nations.
In the 1860s, 25% of the world's mass and population was under a single government, the pre-Dominion-era British Empire. From then onwards, we're broken up into tribal lines across the world. Just look at Europe as an example
True, but doesn't particularly speak towards the current scenario I was referring to. Current consensus among most governments is that the nature of international governance needs to change. There are certain ongoing processes that lead to better consolidation of UN and various other large regional blocks, and the UN existing alone promises a "weak" world government. Imagine something along the lines of an articles of the confederation US.
You can already sort of claim that world government exists, since the UN does, and certain groups are only "recognized" as legitimate governments when they meet certain political conditions. Like, the UN recently carved up Sudan because of ongoing conflict, which reveals the amount of power being consolidated, and Somaliland actually has a sort of independent World Bank delegation, but isn't allowed to have embassies, because its seen as "illegitimate". Climate Change essentializes that in addition to meeting legitimacy requirements governments will have to meet environmental requirements, and the international community (to the extent that it exists) is figuring out how to deal with this issue.
In the future, the thing that will differentiate government's from strong organizations(megacorps, etc) will be the legitimacy and international obligations they must uphold in the UN. There's a current worrying trend of the "unraveling" of state power, rise of multinationals, etc, but I'd expect a pushback by or before the late 21st century. People are typically unwilling to fight wars for corporate reasons, and I think Yergin and Stanislaw correctly assert in the book The Commanding Heights that "few people would die with the words "free markets" on their lips".
Regional block consolidation will definitely be more prominent first though. I'm sort of surprised that the African Union model of communal intervention hasn't been adopted in other places (although I guess few have the need for it), and probably the true emergence of a global system will be predicated on that happening.