Four decades ago the People's Republic of China was a closed and mysterious, even forbidding, society. Mao Zedong and his fellow communist revolutionaries turned an impoverished, backward, authoritarian mess into a starving, retrograde, totalitarian horror.

But the 1970s saw the famed opening to the West. Mao's death a decade later allowed Deng Xiaoping to take control as "paramount leader" and initiate reforms that unleashed the creativity of the Chinese people. The PRC has gone from isolated backwater to emerging giant. The high rise office buildings, luxury hotels, flashy advertisements, foreign automobiles, and traffic jams could belong to any big city in the West. Young people sport trendy hair cuts, stylish clothes, tattoos, and piercings. Mao, the "Great Helmsman," would not recognize today's China.

The international order also is changing. A century and a half ago the U.S. was "rising" in the world. That process forced other nations to adjust. A similar process is happening with the PRC. Its neighbors, as well as the United States, must adjust in turn.

Chinese President Xi Jinping is meeting President Barack Obama in California this week, the first time they will talk as leaders of the globe's superpower and Asia's emerging regional great power, respectively. Much is at stake in their administrations forging a working relationship that can make the international adjustment process as smooth and peaceful as possible.

In May President Xi told National Security Adviser Tom Donilon that "The current China-U.S. relationship is at a critical juncture to build on past successes and open up new dimensions for the future." Those "new dimensions" remain undecided.