1. A legal inequality from 100 years ago. My comments are about the US specifically, no doubt systemic sexism exists in other countries.
2. From your wikipedia link, one of the key arguments against the amendment was that it would imply women could be drafted - "Political scientist Jane Mansbridge in her history of the ERA argues that the draft issue was the single most powerful argument used by Schlafly and the other opponents to defeat ERA".
If you want to show a persuasive (to me) example of systemic sexism, I think you should provide an example that is current and that systemically disadvantages women. If the lack of an ERA does disadvantage women, please explain how.
If you are unwilling to understand the significance of it taking until 1920 for women to receive the right to vote, and the variety of reasons for resistance to the ERA, then, I don't know what to say.
If you haven't, talk with the women in your life you are friends with about sexism and discrimination in the work place.
I think it's a pretty low bar to ask for an example of a current systemic disadvantage that women have. I can point to multiple systemic disadvantages that men have right now - but your examples are from 100 years ago or are very vague. If the systemic oppression of women in the US is so vast as to necessitate laws that advantage or disadvantage individuals based on their sex, then I think it should also be pretty easy to point to.
As far as talking with women about the sexism they've experienced - I've never denied women experience sexism. I've explicitly acknowledged that multiple times. My point is that the sexism they experience is not an organized system of oppression (i.e. it is not "systemic"). There are multiple, explicit, and codified systems that disadvantage men and I have pointed to several of them.
2. From your wikipedia link, one of the key arguments against the amendment was that it would imply women could be drafted - "Political scientist Jane Mansbridge in her history of the ERA argues that the draft issue was the single most powerful argument used by Schlafly and the other opponents to defeat ERA".
If you want to show a persuasive (to me) example of systemic sexism, I think you should provide an example that is current and that systemically disadvantages women. If the lack of an ERA does disadvantage women, please explain how.