Hello Akasaka,
That depends.
When I learned American English, the rule was that a comma is allways required between two independent clauses. However, my young English friends tell me that they were taught never to put a comma before "and." I think that that rule is altogether too general and really applies only to lists, not to independent clauses, but they take it literally.
I prefer the AE-form with the comma -- it makes the sentence pause where a pause is needed.