The problem is not the SEC, which has no jurisdiction over Mona.co or any other EU-based ICO. The problem is the IRS and FATCA, which requires US taxpayers AND financial institutions in tax-treaty countries to report all assets held abroad by said taxpayers. Many banks and other financial institutions abroad simply don't want to do business with Americans, because of the regulatory burden FATCA requires of them, and because the information demanded might in fact violate their own "house rules" about client confidentiality. 

So, Mona.co asked the question to screen out Americans. Otherwise, Mona.co might find it hard to get the EU licensing they need  to carry out their plans. They also might be obligated to return the American investors' funds, which is problem a hassle they don't want to have.

The Polybius Bank people also warned US taxpayers not to join in their ICO for the same reasons.

We need to convince Washington to rescind FATCA, as it has not proved to be effective in eliminating money laundering or  tax evasion. The fat cats can evade the law by creating shell companies and other clever machinery to hide their money. It's honest citizens who are being unduly discriminated against by FATCA, not the crooks.

Incidentally, I wrote about this same subject a couple of days ago.