It's worth reading the specific actions they cite that lower the US's ranking. They include the closure of Voice of America, a government-run propaganda outlet for foreign audiences (and I do think that closure is bad! just not relevant at all to free speech); mergers of several big media conglomerates; not to mention, bafflingly, restrictions on journalism by the Iranian government in Iran, which somehow counts against the US.

None of this says anything about Americans' right to speak freely, which is absolute, unlike in any European country.