Exchanges and casinos block ips from the United States but everyone just uses a VPN, why even block their ips in the first place when you know they are going to do it anyways. I'm guessing they do it so they have some type of deniability?
It's very risky if your country is prohibited or banned from participating in their program be it ICO or gambling, then do not participated at all, because if you get caught that you are using a VPN to hide or cloak your location, they can disable your account and you cannot complain about your funds or you cannot ask for a refund because you have violated one of the rules in their TOS.
Some gambling and ICO can detect your location and they just wait for you to deposit funds before they disable your account, because they know you cannot make a refund.