Bitcoin through Cash App is available to all users except those located in New York, Georgia, Wyoming or Hawaii, according to Square's website.
You can even get a debit card to purchase items using bitcoin. However, you can right now only withdraw and spend bitcoin, you cant transfer bitcoin from other accounts into the Cash App.
This brings bitcoin one step closer to mass adoption. If only they would let you buy Stellar too, I would predict that they will expand the number of currencies supported in the next 12 months, probably with eth next.
https://9to5mac.com/2018/01/31/square-cash-app-bitcoin/