叫独立日为国庆日（节）与思维和翻译无关，它和事实有关。

wikipedia是这样解释国庆节的。

https://en.wikipedia.org/wiki/National_day

“国庆日是庆祝国家或非主权国家的庆祝活动的指定日期。 这个国家可以通过独立日期，成为共和国或守护神或统治者的重要日期（生日，加入，移除等）来象征。 通常这一天不被称为“国庆日”，但可以被视为一个。 国庆节通常是国定假日。 许多国家都有一个以上的国庆日。”

“A national day is a designated date on which celebrations mark the nationhood of a nation or non-sovereign country. This nationhood can be symbolized by the date of independence, of becoming a republic or a significant date for a patron saint or a ruler (birthday, accession, removal, etc.). Often the day is not called "National Day" but serves and can be considered as one. The national day will often be a national holiday. Many countries have more than one national day.”

wikipedia是这样解释美国独立节的。

https://en.wikipedia.org/wiki/Independence_Day_(United_States)

 “独立日是美国国庆日。[2] [3] [4]”

 “Independence Day is the National Day of the United States.[2][3][4]”