At the bilateral level, these retreats have boosted cooperation and mitigated tension. Examples abound. On all three occasions, the two leaders reiterated their desire to reach a high-standard "Bilateral Investment Treaty". After exchanging and revising their respective negative lists, the two sides are now working to achieve this goal.

Military-to-military ties between the countries are an "underdeveloped" area. At Sunnylands, Xi proposed two confidence-building mechanisms (CBMs) to change the dynamics. After the Yingtai retreat, they announced mutual notification of major military activities and a code of behavior for the safety of maritime and air encounters.

A few days ago, at Rose Garden, the two leaders announced the broadening of the CBMs to cover more activities. Even on cyberspace, widely considered a point of contention in Sino-US ties, Xi and Obama have proven critics wrong by showing a readiness to cooperate in investigations and facilitate international negotiations to establish acceptable norms.

Without Sino-US cooperation, it would have been much more difficult to manage, let alone resolve, many regional and global issues. The Iranian nuclear issue is a case in point.

One of the under-appreciated facts about China-US relations is the growing cooperation to meet global challenges, such as the joint response to the Ebola epidemic in western Africa. A key deliverable at the Sunnylands meeting was the joint pledge to phase down hydrofluorocarbons, or the "super-greenhouse gases". At Yingtai, the two leaders went a step further by announcing significant actions to fight climate change, a move that was widely hailed as a game-changer for international negotiations. After their White House meeting a couple of days ago, they gave a clarion call to the world to secure "an ambitious, successful Paris outcome" at the climate conference in December.

Seventy-years ago, China and the US fought alongside each other to defeat a common enemy. Thirty-six years ago, they came together, driven by an alignment of strategic interests. But then, China was just emerging from a tumultuous decade. Today, China and the US have a high stake in each other's success, just as the world has in a strong and resilient China-US relationship, to which the Xi-Obama summits have undoubtedly contributed. We are all better off because of it.

The author is an analyst with the Foreign Ministry of China.