Why has radiation from the Fukushima plant disaster have reached the California coast and not in nearby Asian countries like Taiwan and Phil?

The prevailing high altitude winds travel northeast from Japan, across the North Pacific/Gulf of Alaska, and onto the "Lower 48" of the USA.
You can verify this by observing the departure track of typhoons/tropical storms that impact Japan.
As Cheapest says, the ocean currents also follow this track. Hence the debris from the tsunami keeps washing up off the northern coast of North America.

In WW2, Japan used these prevailing winds to launch balloons carrying high explosives which were shot out of the sky by P-40s near British Columbia and Washington State....Show more

Look at ocean currents in North Pacific. Ocean currents in North Pacific go clockwisely. It goes from Fukushima to California, not from Fukushima to Taiwan/Philippines.
http://en.wikipedia.org/wiki/North_Pacific_Gyre...Show more

It will or some of it will reach the Philippines on curents. It will be more deluted. After it gets down in Mexico the curent turns West and runs North of the Philippines. Be a year yet to get there....Show more