Declaring "Antifa" a terrorist organization makes as much sense as declaring "MAGA" a terrorist organization

I don't actually know what "Antifa" is, if it is in fact anything specific (rather than, e.g., a banner used by many and disparate groups--maybe that was your concern?).

What I did mean is that declaring certain organizations to be terrorist organizations (HAMAS, Al-Qaeda, etc.) seems to be well within the remit of the executive branch.