Seriously, why not?  They don’t have enough money first turn to build anything useful, but moreover, there is nothing they really need to build.  They already have 9 Fighters, 5 Transports, and a ground force poised to easily trample India/China/Siberia/Indonesia.  The thing is that while US may be a threat eventually, you don’t need to worry about immediately building units to counter them.
So, Japan should just buy 3 Researchers first turn.  This will give them about 66% chances of getting a Tech by the beginning of their second turn, whereupon they have 40-50 money to start spending on the results of that Tech.  Moreover, 3 of the Techs are basically I WIN buttons.
Jet Fighters: Your 9 Fighters become as strong as 12, you can also build a good number of them each turn.
LRA: Or as fast as Bombers
Heavy Bombers: Which you can pump out at a rate of 3 or 4 per turn.
As for the less good techs
Improved Shipyard: Still a solid tech, allow you to build large fleets
Super Subs: If you get this, just spam a large number of Subs, then sink any Destroyers or Fleets in general that come into range.  It might not stop the US, but it will probably stall them for an impressive amount of time.
Radar: This one won’t stop Fleets, but at least it will block Bombers, especially Heavy or Long Range ones.