The term antifa, which is shorthand for antifascist, describes both an ideology and a protest movement, rather than an organization. Local antifascist organizations, some of which refer to themselves as antifa, do exist throughout the U.S.
RAND Corp., a non-profit, non-partisan think tank, describes antifa as a "loosely oriented movement." On the national level, antifa is not an organization with named leaders, bylaws, or members, but a term describing largely unaffiliated groups and individuals that share a militant opposition to fascism. Even local antifascist organizations are largely devoid of a leadership structure, and generally focus on coordinating protest efforts and connecting like-minded activists.