Even if your TV set remains unharmed, it's highly probable that the TV set can not be tuned for TV channels / programs in Japan.
A switch from analog to digital TV broadcastings is now being made in U.S.A and in Japan.
A U.S.A-spec analog TV tuner does not cover some channels in Japan.
On digital TV broadcastings in Japan, almost all TV programs -- including news shows -- are coded for copyright protection, also for prevention against free view as to pay programs. Such coded programs can not be watched without TV receivers adopting a decoding system.

Generally speaking, a concept like "a voltage difference between U.S.A. and Japan is negligible" is not correct. There may well be cases where the difference is causing a trouble, while the user doesn't notice it because the electric appliance is apparently working normally.
Whether frequency difference (60 Hz in U.S.A., 50 Hz in Tokyo) pose a problem depends on models. That's a question to be answered by the manufacturer or the vendor who officially offers technical supports in U.S.A. on your TV set.

When all the problems driving from differences in power supplies are settled, if your TV set has audio and video input lines with jacks common in Japan, maybe you can use it as a monitor connected to a Japan-spec digital TV tuner kit.

Anyway, the first principle is to use Japan-spec appliances in Japan, U.S.A-spec appliances in U.S.A.
I do not recommend using your TV set in Japan unless that has passed checks by a certain professional.

But like the guy above have said, you may have a problem with tuning into Japanese stations. You can always hook up a separate TV tuner that will go into the TV. (Something like this: http://www.yodobashi.com/ec/product/100000001000953229/...