

In Australia, there is a strong presumption towards keeping left as a pedestrian (and overtaking on the right - e.g. etiquette on escalators is to keep left, but if you are walking up the escalator, overtake to the right).
In some particularly busy places (especially on shared footpath / bike lane zones) there are even arrows on the pavement to ensure tourists know what side to keep to.
There are always a few people (probably tourists) who don’t follow the local etiquette.
I think it was a 18th century British fad that spread to America - for example, look at the date on this London newspaper from 1734:
It didn’t make it into legal documents / laws, which still used the more traditional format like: “That from and after the Tenth Day of April, One thousand seven hundred and ten …”. However, the American Revolution effectively froze many British fashions from that point-in-time in place (as another example, see speaking English without the trap/bath split, which was a subsequent trend in the commonwealth).
The fad eventually died out and most of the world went back to the more traditional format, but it persisted in the USA.