An increasing number of ICOs are choosing to disallow US investors from participating. For those of you on those management teams, or those of you with connections to those teams, I urge you to consider the following:
1) Presumably, disallowing US based investors is for the purposes of avoiding US securities laws. However, many other countries around the world have securities laws as well. If for legal compliance purposes, the determination has been made that your ICO is a securities offering under US laws, it's likely that it would also be considered a regulated securities offering under other jurisdictions.
2) There are some reasonably easy ways to be able to accept US based investors. Please refer to https://steemit.com/crypto-news/@jrlmaker/securities-exemptions-for-icos