According to this[1], with 140k you're in the top 5% Americans, so you're not far off... but regulating immigrant's salaries on a regional basis seems unfeasible, as they're free to move anywhere in the country AFAIK, just like any other US resident.
Why is it unfeasible? Companies give cost of living raises - and pay cuts - depending on where someone lives in the US. If companies can figure this stuff out, why can't the government? Don't companies get their cost of living data from government agencies anyway?
As someone who lives in a different state I object to someone who is otherwise equal in ability to me earning more for the same work (I have personal reasons to not want to move to CA). I understand why companies do it (only those who have a reason they need to stay in CA - why google doesn't move doesn't make sense), but I will object to my government encouraging the situation even more. My representative needs to be sensitive to that.
This isn't something special to the US, though, and i'm pretty certain if it was changed so that folks in Indiana made the same money as California, folks in California would make worse wages.
The truth is, though, that folks getting paid well in Indiana can generally live better on the lower wage simply because things are that much cheaper. Perhaps you wish to subsidize living in the more expensive areas and increase the safety net?
Maybe you should place some pressure on companies to move headquarters into more affordable places. Lots of places have international airports, after all, so that shouldn't hinder folks much.
Do you think your representatives gives two farts about what folks in a different part of the country are paid so long as folks in his or her district are living well enough? Or should folks in the area living well be enough of a concern?
Do you have solutions for these things that are fair to the folks needing to live in the expensive areas (poor folks have little to no choice in the matter)?
Maybe something like upper 2% of salaries in the county.
A fixed number will never be appropriate for all the areas in the US, and a fixed number will always need to be adapted.