Accreditation of US universities is carried out by private, non-governmental organisations on a regional basis, rather than a centralised government body.
If you need to simply verify that a US university is accredited, you may wish to search the following databases:
Please note if you need a document attested or verified, you may wish to use services provided by the Office of Authentications of the US State Department or a company that can coodinate this process for you such as Speedy Egger. (Please note the Fulbright Commission does not endorse any university, product or service.)