It's perfectly legal to set up communist communes in the US, and there have been no shortage of attempts. They all failed. It's hard to claim they haven't been given a chance.
There are plenty still in operation. However, any of the attempts which actually posed a threat to the system were usually violently suppressed. See for example the unlawful assassination of Fred Hampton or the MOVE bombing. There is often a big difference between what is legal and what is practically implemented when it comes to these issues.