In how many countries does the term 'Black Friday' have cultural significance? Where, and how, did the phrase originate?

Black Friday is mainly a thing in the US, but several other countries, including Australia and South Africa, have started observing it too. The origin of the name Black Friday is unknown. but Wikipedia claims that the most popular theory is that it came from how retailers used red ink to show negatives and black ink to show positives in their records.
https://en.wikipedia.org/wiki/Black_Friday_(shopping)

In Germany, Black Friday was launched in 2006. It has been so successful that many stores have introduced a "Black Week" starting a few days before Black Friday and ending on the following Monday, called "Cyber Monday".