global government

Bingo.

Pie in the sky at the moment, but consider the advantages:

Equalisation of opportunity - people could move as freely as capital, subject to common sense limits
The instant removal of a $1 trillion annual military tax
Closing of all so-called off-shore tax loopholes, which would put yet more wealth into play for productive social investment

The current system of competing nation states is ruinously expensive.

Of course you'd need the strongest democracy in history to prevent a slide towards feudalism and oligarchy. You could create that with absolute limits on personal wealth and influence and semi-random sortition of public representatives.