Spin Palace is regulated by Malta and powered by Microgaming casino games. Both Malta and Microgaming do not accept citizens from the United States of America.
I sent an email to the Spin Palace support to get a clear explanation. Here is their answer :
From your email we understand that you are unable to register.
Please be advised that due to the Safe Ports Act of 2006, we no longer accept players from or operate in the United States of America at all, as we are not a US-Based Casino.
We would like to refer you to one of our preferred partners, ClickFun Casino, by visiting our website on your PC - www.clickfuncasino.com who do operate in the United States of America.
Should you require any further assistance feel free to contact our friendly help desk. We are available 24 hours a day, 7 days a week for your convenience.
As part of the US gambling law, Spin Palace preferred to step back from the US Markets. However, some online casinos still continue to accept US citizens. Check our top 3 US Casinos.
Technically, you could play to Spin Palace if you signed up from abroad. For instance if you are in vacation in Costa Rica or in Mexico, you could play to Spin Palace while you drink your Margarita. However, you should not use a US address and an american credit card (from Chase for instance).
This is the same problem as "signing-up from abroad". You could use a VPN to play to Spin Palace, but you would need to have a real address outside of the US (with electricity bill at your name for instance). If you have a brother abroad, for instance in the Brazil, it could work. Otherwise, in case you win a $0,000,000 jackpot, Spin Palace could block your funds..
We know that Bovada is currently accepting US citizens. It is powered by Top Game software and offers a nice welcome bonus.