Warren Buffett once told me that his favourite investments were not so much bets on the US as bets on the ability of American companies to continue exporting capitalism around the world.

Berkshire Hathaway holdings such as American Express, Coca-Cola, Kraft-Heinz and Procter & Gamble were huge global franchises. An increasing amount of their growth came from emerging markets, while they still paid out a reliable dividend. They were, he said in 2012, safer even than US Treasury bills.

What a difference in perspective a few years can bring. Put aside the recent challenges faced by individual companies including Kraft-Heinz. These days, the entire wisdom of hedging via the equity of US multinationals is suspect. It is now quite unclear how — or, in some sectors, if at all — cross-border business will be conducted in the years ahead.