Answer: they are both victims of global warming.
Tibet and the western states of the U.S. are mountainous regions and the sources of major rivers that drive national economies and support significant aquatic biodiversity. The melting glaciers of Tibet form the headwaters, and much of the flow, of the Yellow and Yangtze Rivers of China, the Brahmaputra of Bangladesh, and the Mekong of southeast Asia. The Yellow and Yangtze are, of course, the two most important rivers of China; powering huge hydroelectric projects such as Three Gorges Dam, providing water to coal processing facilities, water to cities and water for agriculture. In the western U.S., mountain streams coalesce to form the Colorado, Rio Grande, and Columbia Rivers. They power massive hydroelectric projects such as Hoover Dam and provide water for agriculture and for rapidly growing cities.
All these rivers are drying. Rapidly melting glaciers in the Himalayas provide a short-term increase in flows for Asian rivers, but the long-term prognosis from climate models for both regions is for steadily decreasing snowfall, increasing temperatures and declining river flows. This is a clear example where failure to reverse global warming will have massively negative economic consequences. China and the United States could both benefit by collaborating to find coping strategies to deal with long-term drought.
References: IPCC 2007; Rogers, P. 2008. Facing the freshwater crisis. Scientific American (Aug. 2008) 46-53