It takes so many turns for most units to get from Europe to Asia, or the other way of travel.
By mid-game you can have a couple Japanese tanks/mechs in central Russia, but they are of minor benefit in most matches as they are less effective than Italian can-openers due to turn order.
In regards to naval units, it is such a long path from one theater to the other that I have never found it worth the effort to do the long journey for the Axis. It is different for the Allies where the Indian Ocean fleet could go through the Suez and meet up with the Med forces, or the other way around.
Air power is where you can have a more practical impact. Having a couple Japanese bombers targeting factories in Russia or Egypt is helpful, although you won’t have enough fighter escorts to raid Moscow in many matches. Getting 1 or 2 German bombers to Asia is crazy good as the Allies won’t be able to ship block the Japanese fleet and hence are forced to be much more cautious in their positioning. This was a key component in my recent OOB championship match.