I think the Know Your Customer also known as KYC itself can help in this issue. Even when you are using VPN, still the KYC can help.
What is with this comment? it doesn't have any relevance to the question. Moving on, yeah you are actually creating a fraud by escaping the RULE they have provided. As far as I know KYC needs some verifications e.g. passport, I.D. so you still need to submit all this information even if you are using VPN's.
I do not see a clear prohibition for US citizens to invest in ICO. However, if such a ban exists, entering the ICO campaign and investing its funds using various VPN programs in any case will not be considered fraud. Fraud is deception or abuse of trust in order to acquire another's property. In this case, no one else owns property, and therefore there will be no fraud. If there are specific rules prohibiting citizens from investing in the ICO, they can also be sanctioned for those who violate these rules. If no sanctions are established, then there is a ban, but there is no punishment for its violation.
There might not be a clear prohibition towards to this matter but we eventually see that some ICO's now are prohibiting American citizens to invest into their project which we can presume that they are really imposing such law.It might not be considered as fraud but eventually a violation that can lead up to further consequences that you might obtained on opposing such laws being implemented.