Fascism is notoriously difficult to define. There’s a huge amount of contention on it among historians, but one definition I like is Rodger Griffin’s. In his definition the core ideology of fascism is
(i) the rebirth myth
(ii) populist ultra-nationalism
(iii) the myth of decadence
I think the MAGA movement pretty transparently meets all 3. The rebirth myth is literally in its name, the movement is pretty openly populist and ultra-nationalist, and decadence is how they describe their enemies (e.g. their rhetoric around trans and queer folk).