I’m not American but Dutch, but our far-right government also really hates Antifa so the answer is probably similar.

1. Antifa is anti-fascist, yeah. But the name is most often not used by all people who are anti-fascist but rather by a rather extreme subgroup of people who have a tendency to escalate protests into riots. They often seem to fight for something good, but not really with the means that are approved by the more centre-leaning average people.

2. Both MAGA and the Dutch far right are also a bit fascist, although MAGA is more advanced in that regard, so they probably don’t really vibe with anti-fascism anyway. It’s all populist politics. They outlaw the “scary left-wing terrorists” to both vilify the left and show their voters that they care about law and order.