If I'm not mistaken, China had the navigational and shipbuilding skills to cross the pacific, so why didn't they?
Check out this answer by /u/fishstickuffs:
Did Zheng He ever reach the America's?
In short,
China didn't colonize because it had no interest in colonizing, and little to gain from colonizing.
EDIT: There's also an FAQ section on this that I completely overlooked. Oops :P
Check out various other answers from out FAQ:
Why didn't China join the rush to set up colonies in the New World? by /u/cthulhushrugged
Why didn't the Ming Dynasty in China colonize the Americas during the Age of Discovery (~1500s)? by /u/cee2027
Why didn't China set up settlements in the New World like Europe? by /u/lukeweiss
Why didn't China colonize more islands in Oceania like Taiwan? by /u/ashkenazeeyankee and /u/roma_victrix
Was China's influence on southeast Asia ever comparable to European influence in Africa and the Americas in the age of colonization? amazing answer by /u/pangerandipanagara
How come China did not expand outwards like other empires through out history? was China ever an empire? by various users