I cheered when John Bogle said it's okay to hold ETFs for flexibility.
He brought up many points in favor of 0% international (disclaimer: I disagree!)... here's a couple:
1. US market regulations. China halted trading for a month, the US hasn't done that. Other countries could prevent investors getting their money back, which is less likely in the US.
2. Buying international developed markets invests 48% in 3 countries: Japan (22%), UK (18), France (8%). He highlighted Japan's demographic problems with an aging population, where the US has less of a problem. He mentioned the UK doesn't know if it will be better within EU or outside it. And he poked fun at how often the French shut things down. But he's trying to express the conditions in the US, for investment, are better than these 3 countries, which are roughly half your international developed investment.
While I disagree with John Bogle's stance on 0% international, I like to see his argument so I know what I'm rejecting.
EDIT: John Bogle recommends a few books: "The Intelligent Investor" (4th ed), "A Random Walk Down Wall Street", "Against the Gods", "Four Pillars of Wisdom".