The American legal theory of employment has always viewed the relationship between employer and employee as one between equal where each can negotiate for what they want from each other. True, that may not be the reality, but in a sense both parties exchange something of value (talent for money, etc.) with each other and both have the freedom to change their minds, as in employees can quit and employers can fire.
Salaries or wages are one of the items expected to be negotiated and, in negotiations, if conducted fairly, some parties may still obtain better results than others. That alone is not a legally correctable matter. However, there may be facts here which someone like me, online and only obtaining a very limited amount of information can be able to learn and speak about to provide information on. There may be certain aspects which we have not discussed that may affect the legal abilities for redress here which my limited view cannot provide information about. There is often, in situations where beliefs of unfairness exist, the potential for legal redress, but you may need to speak, privately with an attorney in your state who works in employment areas so you and he/she can thoroughly discuss any potential abilities for a claim. For example, if there are any employer documents which promise or indicate that salaries will be equal or based on similar factors that may create a contractual breach claim for failure to honor such promise or policy.
For legislative interest, I cannot speak to but you can contact your own legislators, or their aides and offices, to discuss this issue with them and see if they can work with you on a proposal of some kind.