Maybe Portugal early on? After them, definitely the Dutch, and if after 1850, the British. I don't know if too much would change other than some more small islands being held by Europe, but I'm not too knowledgeable on East Asian history.
If the Portuguese conquered Ryukyu in the 16th century, the Ming would ban all trade with them even more strictly than OTL. They would be forced to bend the knee and abandon Ryukyu so they could get a trade deal with China.
If Europeans conquered Ryukyu in the 17th century, Japan would kick them out.