Why is Tokyo colder than LA?

It is noticeably further north, for one thing. LA is a little over 34 degrees north of the equator, Toyko is at about 35.7 degrees north.

The rest of the equation has to do with ocean and atmospheric currents and is complicated. In the northern hemisphere temperate latitudes, the east coast of a landmass tends to be cooler than the west coast at the same latitude (Boston, for example, receives a lot more snowfall than Seattle, though Seattle is a few hundred miles further north and receives considerably more precipitation overall).