Maybe. In practice, however, even in the US there are and there have been censorship instruments, from the FCC all the way to Sen. McCarthy and Hoover. Today, US military personnel and civil servants are "protected" from wikileaks material by blocks at the network level. Federal pornography filters have been proposed several times, and on occasions it looked like they would become a reality. The US Constitution might be more benevolent than average on freedom of expression, but it doesn't mention TCP/IP anywhere.