In 1993, when the first TOP500 list was published, China was not even on it.
Ten years ago, in 2006, China had 28 systems on the list and the U.S. dominated with 298 systems.
Five years ago the count was China 61 and the U.S. 255.
As of June 2016, the tables are turned. China has 168 systems on the list and the U.S. dropped to #2 overall with 165 systems.
The US stopped deploying large systems and let the US supercomputer lead slip away.
SOURCE - InsideHPC