The attacks took place around the time of a neo-Nazi gathering, and the perpetrators were reported to have used metal bars and hammers.
Legal proceedings are ongoing in both Germany and Hungary.
The State Department’s move comes just days after populist-nationalist Hungarian Prime Minister Viktor Orbán visited his close ally, U.S. President Donald Trump, in Washington.
The designation also follows Trump’s September executive order labeling Antifa a domestic terrorist organization in the U.S. Orbán later said he would follow “the American example” and classify Antifa as a terrorist organization in Hungary.