The "wage gap" people speak of is not a wage cap at all. It's based off of the annual earnings of men and women. Men do annually make more money than women because they dominant areas such as STEM degrees and higher earning degrees where women dominant in areas like nursing, cosmetology, etc. There's always exceptions to the rules obviously but I'm talking about on average.
I also want to point out like what OP said, women take off more time annually then men do. So of course we are going to make less if we pursue degrees that don't make as much money or if we take more time off. Again this is annual... this is not per hour. Men and women make the exact same money per hour for the same position, with the same qualifications, starting at the same time.
ALSO, before anyone mentions it, please do not pull the "we don't have the same opportunity" as men card. In many STEM programs across the country, you are at an advantage if you are a woman in terms of getting in because they need and want women to join such male dominated fields. The majority of us women just don't because most of us find interest in other things and there's absolutely nothing wrong with that. As women, we actually have advantages in getting into college in general over men, look at the stats. If I remember correctly there are more women ever going to college and actually more than men, which is a good thing!
And women overwhelmingly dominate the nursing field and also "manager" or higher up positions within the nursing field. So to act as if it is normal for men to advance much quicker than we do in the nursing field would be false.
I am by no means trying to downplay what women have gone through in the past in this country and are still going through in different parts of the world. My point is if you go out searching for something, you're probably going to find it (men making more than women) but the overwhelming majority of professions are very equal and almost favor us women today when it comes to opportunity.