Matthew Barney’s vastly ambitious “Cremaster” cycle, 1994–2002, was finished and presented in that window between 9/11 and the financial collapse of 2008. Not surprisingly, several critics saw it as a bloated corollary to American pomp and male triumphalism. The US has faced some harsh truths since then, but Barney’s follow-up project, “River of Fundament,” 2008–14, is just as grandiose: a series of epic performances, a five-hour-long film-cum-opera scored by Jonathan Bepler, drawings, storyboards, and a group of monumental sculptures. As with “Cremaster” there are cars, metamorphosing figures,