SHANGHAI, June 16 (Reuters) - U.S. memory chipmaker Micron (MU.O) said on Friday it was committed to China and would invest 4.3 billion yuan ($603 million) over the next few years in its chip packaging facility in the Chinese city of Xian. The company has been targeted by China's cyberspace regulator, which last month said the firm, the United States' biggest memory chipmaker, had failed a network security review and that the regulator would block operators of key infrastructure from buying from the company. Micron made no mention of the review's decision in its Friday statement, posted on WeChat. "This...