The average Japanese employee works less hours per year than the average American, on what comes down to having an additional two weeks off per year (1713 vs 1783 hours worked annually [1]).
Of course, with statistics like these one has to consider the fact that second-income earners working part-time jobs make the statistic skew low, which means that in countries where wages are high enough to feed a family with only one parent working, the numbers will skew higher despite less actual hours worked. I am note sure to what degree the statistics address this issue.
This uses the official numbers for average hours worked in Japan, which are definitely not accurate as a lot of overtime is unreported (and unpaid), especially at particularly bad companies.
Employee is now a loaded word. Does this statistic include contractors or just hired "employees"? A great many workers in the US, from delivery drivers to doctors, are no longer actual employees. Do their hours count?
Not every company gives summer and winter breaks. These companies also have awful leave policies (on average less than 10 days for companies with breaks). None of them provide sick leave (you must use your standard leave for sick days).
Overtime, until very recently, went uncounted and was unpaid. So the statistics you quote are almost certainly very wrong.
Recently the government has been cracking down on overtime (and especially on unpaid overtime), and requires companies to track overtime. It's only considered excessive overtime if it's more than 45 hours extra hours a month, to give you an understanding of just how much people are working.
Recently at the same time, gov also enforces every employee must take at least 5 leave days in a year. What's happened in smaller companies is that they removed holidays at summer (exact: Obon) and at the end of year, and enforces employee to take leave days at the removed holidays exactly. Awful.
Japan also doesn't report its work hours fully. The notorious 12 hour work days in Japan are not commonly reported as such. American workers by contrast are (properly) penny counters when it comes to overtime, shift differential, et al. Every hour they work over is going to get counted and credited. The US has stricter labor laws at this point than Japan does.
Of course, with statistics like these one has to consider the fact that second-income earners working part-time jobs make the statistic skew low, which means that in countries where wages are high enough to feed a family with only one parent working, the numbers will skew higher despite less actual hours worked. I am note sure to what degree the statistics address this issue.
[1]: https://en.wikipedia.org/wiki/List_of_countries_by_average_a...