Summits are not just — or even mostly — about what happens in the formal leaders’ meetings. What happens on the sidelines often has the largest effect on steering the course of international politics. This is the first year that the G20 summit could end up as a failure, advancing little in the way of substantive progress on the global governance agenda, chiefly owing to the group now having to contend with Donald Trump taking America’s seat at the summit table. Trump’s ‘America First’ agenda — typified by its economic protectionism and rejection of the established multilateral order — is entirely antithetical to the G20’s previous commitments to reject protectionism and safeguard the liberal, rules-based, multilateral governance order. This year’s G20 …