In the US for every employer I've seen, holiday pay is usually 8 hours of straight time (assuming you have an 8 hour shift) plus 1.5x for the hours you worked. So if you worked your normal 8 hour shift you get 2.5x pay. But it's not. If you worked less then 8 you get 8 hours straight plus 1.5x the hours you worked. It's also common that if you worked 40 hours before the holiday that straight time becomes overtime. Usually only applies to Thanksgiving/black friday. And occasionally Christmas when it falls towards the end of the week.

Needless to say this varies among employers. If you have a union you likely get double or even triple time for hours worked on a holiday, but likely still the same straight time pay for the day itself. Legally the company doesn't have to pay anything extra for holidays for time not worked.