The Collaborative International Dictionary of English v.0.48:

I \I\ ([imac]), pron. [poss. My (m[imac]) or Mine
   (m[imac]n); object. Me (m[=e]). pl. nom. We (w[=e]);
   poss. Our (our) or Ours (ourz); object. Us ([u^]s).]
   [OE. i, ich, ic, AS. ic; akin to OS. & D. ik, OHG. ih, G.
   ich, Icel. ek, Dan. jeg, Sw. jag, Goth. ik, OSlav. az', Russ.
   ia, W. i, L. ego, Gr. 'egw`, 'egw`n, Skr. aham. [root]179.
   Cf. Egoism.]
   The nominative case of the pronoun of the first person; the
   word with which a speaker or writer denotes himself.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Us \Us\, pron. [OE. us, AS. ?s; akin to OFries. & OS. ?s, D.
   ons, G. uns, Icel. & Sw. oss, Dan. os, Goth. uns, L. nos we,
   us, Gr. ? we, Skr. nas us. ????. Cf. Nostrum, Our.]
   The persons speaking, regarded as an object; ourselves; --
   the objective case of we. See We. "Tell us a tale."
   --Chaucer.
   [1913 Webster]

         Give us this day our daily bread.        --Matt. vi.
                                                  11.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

We \We\ (w[=e]), pron.; pl. of I. [Poss. Our (our) or Ours
   (ourz); obj. Us ([u^]s). See I.] [As. w[=e]; akin to OS.
   w[imac], OFries. & LG. wi, D. wij, G. wir, Icel. v[=e]r, Sw.
   & Dan. vi, Goth. weis, Skr. vayam. [root]190.]
   The plural nominative case of the pronoun of the first
   person; the word with which a person in speaking or writing
   denotes a number or company of which he is one, as the
   subject of an action expressed by a verb.
   [1913 Webster]

   Note: We is frequently used to express men in general,
         including the speaker. We is also often used by
         individuals, as authors, editors, etc., in speaking of
         themselves, in order to avoid the appearance of egotism
         in the too frequent repetition of the pronoun I. The
         plural style is also in use among kings and other
         sovereigns, and is said to have been begun by King John
         of England. Before that time, monarchs used the
         singular number in their edicts. The German and the
         French sovereigns followed the example of King John in
         a. d. 1200.
         [1913 Webster]

WordNet (r) 3.0 (2006):

U.S.
    n 1: the executive and legislative and judicial branches of the
         federal government of the United States [syn: United
         States government, United States, U.S. government, US
         Government, U.S.]
    2: North American republic containing 50 states - 48
       conterminous states in North America plus Alaska in northwest
       North America and the Hawaiian Islands in the Pacific Ocean;
       achieved independence in 1776 [syn: United States, United
       States of America, America, the States, US, U.S.,
       USA, U.S.A.]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

US
       Unit Separator (BTX, VPCE)