There's absolutely no fraud in using a VPN. You could get the same result by traveling abroad, but there could be a fraud if falsify your identity, your address or your citizenship.
There are no US laws banning ICOs to Americans, rather possible future regulations regarding security classifications for ICO issuers. This is why they ban American participation. If you lie and get into the ICO, wouldn't that be contractual fraud? What I've gathered the only way you'd get in trouble legally is if the ICO issuer started a civil lawsuit against your participation.