If you already have spotify USA based account then just follow the steps from Invitation Link. Else follow instructions given below:
1. Launch any kinda VPN which has USA Server
2. Connect VPN with USA IP
3. Go to Spotify Website.
4. Edit Profile -> Change Country to USA.
Now Click on Invitation Link given below…
Invitation Link : https://www.spotify.com/us/family/join/invite/840c9581074b1yZ/
Address : Philadelphia, PA 19104, USA
N.B. : Only first 5 members will be able to join this link. So, do hurry if you need it :)