There is little consensus between the dichotomy of holiday and vacation. In Australia we use the term 'holiday' to denote a public holiday as well as an extended holiday for travel. I was under the impression American's subscribed to vacation - e.g. "summer vacation".
I propose the following: a day that everybody gets off such as Christmas or New Years Day is a celebration or a holiday: we are celebrating the specific event, and it is also a holy day. A vacation, however, is when you take days off and decide to travel - you vacate.
Thanks!