The OP's "across the US" includes a lot of casinos that aren't in Vegas. I've never had a problem getting racks at any casino in AC or Biloxi, for example.I've been told over a dozen times from cage cashiers and managers in a number of LV casinos, they cannot sell chips. Like you cannot give them a hundred dollar bill and get a rack of chips from any cages outside of a poker room.
Just trying to help pass on info from what I've encountered in Vegas.
And I've gotten racks of chips from the main cages at numerous Vegas casinos, including Luxor, Flamingo, Venetian, Cosmo, Aria, and a few downtown. Some don't, like Paris, but some do...