As @jgeltzer just pointed out, US law provides for designating “foreign terrorist organizations” & “specially designated global terrorists.”
It doesn't provide for designating anything just “a Terrorist Organization”
During the midterms, the "enemy" was the homeless migrant families.
Now the "enemy" is other Americans, but in both cases, the danger posed by the enemies is invented. There is no evidence that "Antifa" organized the looting.