Not in literal sense, I think, albeit I wouldn't exclude an option of more or less codified imperial status. America can transform into Empire (or, more likely, fail to do so) without bothering itself with formal restructuring of judicial frameworks. Compare Russian Federation, where federalism began to dwindle already in 1993, to progressively become all but extinct under Putin after 2012. I think you immediately agree with me in that Russia nowadays could be considered an empire, and one of the most centralized in relatively modern history at that. Despite this, Russia preserves formal status of Federation and even clumsy, mostly inherited from the USSR, internal division into federal districts, which, though, have in practice hardly more meaning than titular sees, as they don’t have significant competences of their own. Moreover, there are quite a lot of constituent entities in Russia that are formally designated as republics, and one of them, oil-rich Tatarstan, even still has its own President. So what? After brief affair with federalism and self-sufficiency in 1990s, marked by grievous poverty and peripheral wars in Chechnya and Dagestan, they promptly coalesced back under aegis imperial in all but name.

Also, if America manages to transform into Empire, it also will mean that, paradoxically, it cedes vestigial pretenses to restore that glorious unipolar moment that marked historical extremum of control that any great power executed upon Earth.

See also CoDominium from Larry Niven & Jerry Pournelle’s novels as a possible exemplar.