CD players sold in Japan can work in US with no problem?

Sorry but it is well known over-voltage will damage electronics.

Not in a cd player or dac, as every separate power supply block in them is regulated. 
The only thing is the mains transformer "if" it can't handle the extra heat, if not over spec'd. 

Assuming the player uses linear voltage regulators, which is a good bet, running the player with 20% more AC voltage than it is nominally intended to be used with will cause the amount of power that is dissipated by some of the parts in the regulator circuits to increase to levels that the designer most likely didn’t anticipate. Consequently both the temperature of those parts and the overall internal temperature of the player will increase to unanticipated levels. Also, of course, the voltages seen by the power transformer, by capacitors in the power supply, and perhaps by other components will increase, relative to what the designer anticipated. None of those factors are good news with respect to long term reliability.  And conceivably with respect to sonics as well.

In addition to the converter that was suggested by Elizabeth you can find inexpensive converters here:

https://www.voltageconverters.com/

Regards,

-- Al

Many thanks.
So far, I have purchased a few electrical items from Japan, assuming that 100V would be no problem with 120V. They were all cheap electric devices under $100, and used very occasionally, and I haven't had any problem so far.
I was looking for something over $1K Marantz CD player from Japan and I wanted to make sure that it would not have any problem. It appears like I'd rather look for something else made for US usage.

I have a few portable Panasonic CD players made in Japan. Great sound and no voltage issues. 🤗

Geoff: Modern switch-mode power supplies are often auto-ranging as far as input voltage is concerned. You would need to check the labels to be certain. 

As Al wisely pointed out, the power supply in the CD player is likely a linear power supply, and designed to operate within specific tolerances for the target market. Most audio gear is made with different transformers for different markets. Depending on regulatory requirements in electrical codes, they may have specific requirements for switching the hot -and- neutral wires, fusing and depending on mains voltage and sometimes frequency differences in some parts of the world, the primary windings and magnetic circuit in the core of the power transformer will be rated for different voltages and frequencies. Over-powering a linear power supply causes rectifiers, ballast resistors and regulation circuit power transistors to run hotter than they were intended to. This heat leads to premature failure and possible catastrophic failure or 🔥 fire 🔥 hazards. Then, there is also the issue of filtering capacitors running over voltage tolerance, and over-heating and bursting or catching fire. This is because in analog electronics, some power supplies are crudely regulated, counting on line voltage to stay relatively close to design and working the filter capacitors very hard without voltage regulation. These cautions explain the real value of power conditioners that mitigate input voltage variance to our expensive gear.