It's not a crime in itself to say "Glory to ISIS!" but if you say it publicly, it will put you on the radar of law enforcement agencies like the FBI who will entrap you and then use your "Glory to ISIS!" post as evidence when they charge you with providing material support to terrorists.
You can find plenty of indictment PDFs on justice.gov that reference "social media posts in support of ISIS."
You can find plenty of indictment PDFs on justice.gov that reference "social media posts in support of ISIS."
Are there any that only reference social media posts in support of ISIS? You could use them as supporting evidence of a crime but they are not a crime in and of themselves.
Sorry, I edited my post while you were replying and clarified that (and then edited it again to restore the quote you were replying to, lol). It's not a crime in itself, but it puts you on the radar to be entrapped and later charged with a crime.
Oh, yeah, I definitely can't see the parents being arrested, even if their kid went through with a terrorist attack. We don't even arrest the parents of school shooters. In some rare cases of juvenile radicalization, maybe the prosecutor would refer the case to CPS, but only if they thought the parents were somehow responsible for causing the problem in the first place. But if there is an actual problem then they'd throw the kid in jail, so there would be no need for CPS.