In the USA do you have a law which regulates the opening times of your stores on Sundays ?
This is something regulated at the state or local, not national level here. In the south, where I am from, Sunday closing laws were once common, but not so much anymore. As Aunt Bea says we called these the "Blue Laws", not sure why.
In Utah, where I live now, there has never been much legal regulation of closings and openings. However the local culture is predominately Mormon and they observe Sundays as a day of rest, so lots of things are closed voluntarily, on Sundays. Most of these are businesses owned by observant Mormons. Used to be a small grocery store in Ogden, the "California Free Market" that advertised they never closed and had not since the end of WWII. However they were eventually closed, for good, by competition from the big chain groceries.
As a note, I am not Mormon, never could understand how people believe as they do. However I like Mormons, they are good people and I have a lot of Mormon friends. I now live in a small town that is probably 99% Mormon, in fact I do not know of another non-Mormon family in town. We all get on just fine, I like it here (except for the cold winters). So I speak freely of and about the Mormons, but do not intend to reflect any negative feelings about them. Oh, and apparently we are not supposed to call them Mormons anymore, not sure why and after so many years I have not stopped. Not quite sure what we are supposed to call them, Members of the LDS Church or something. The name Mormon is just too easy for me to say, and I do not believe it is in any way derogatory, certainly not meant so by me.