Disclaimer: "I am not a financial advisor or legal professional. I'm present here posting only to state my opinion. Please seek a professional in your jurisdiction for any financial or legal advice."

  Simple, the U.S has agencies within place to protect their citizens wellbeing from fraudulence and other thievery.
The United States SEC (Securities & Exchange Commission) has tough policies in place that make offering of securities illegal, unless registered and successful approved with their agency first.
   ICO'S who offer tokens as utility, are usually deemed as securities because the token may offer a dividend or other incentives with the promise of profit. This domain of security falls within the realm of the SEC.
    In order to avoid a tiring legal battle with the U.S, other countries wherein the ICO'S are held consult with their legal teams to design disclaimers for would be investors whom are looking to invest in their company, dissuading them from participating.