The admission process in US universities uses multiple criteria; SAT forms just one part of it. And SAT is not required at a growing number of institutions -- especially liberal arts colleges.
In spite of the small (and diminishing) role of SAT and other such exams in the admissions process, they have received -- and continue to receive -- an amazing amount of critical scrutiny by experts. Inside Higher Ed has a story on the latest such scrutiny, led by Richard Atkinson,
ex-Chancellor ex-President of the University of California system; it was during his tenure earlier this decade that the UC system threatened to stop requiring SAT. Here's an extract from the story:
In his talk, one of Atkinson's themes was that the underlying flaw of the SAT is that it was designed to measure student aptitude, and remains so, long after the College Board removed "aptitude" from its name. Atkinson said that there is a much higher validity to tests based on actual knowledge learned in courses, and that -- grade inflation being what it is in high schools -- admissions officers genuinely benefit from a national tool to compare students boasting A's in calculus, chemistry or French at high schools where an A may mean different things. (Despite those concerns, Atkinson stressed his view that grades in college preparatory courses are the single best way to predict college success.)