On my Mac calendar the week starts with Sunday.
The fact that american calendars start on Sunday, even tho everyone considers sunday the end of the week, is a little 'tell' of Jewish influence.
Why do Jews have to come in to this?
You can thank the Jews for the whole idea of a 7 day week with a day of rest. We got the idea from G-d, Jesus kept shabbat, you guys got the idea from him, although someone changed it to Sunday, and the Muhamad liked the idea too and used it in Islam, changing it to Friday. The 7 day cycle has no astronomical logic. It was a gift from the creator.