The Collaborative International Dictionary of English v.0.48:

Americanize \A*mer"i*can*ize\ ([.a]*m[~e]r"[i^]*kan*[imac]z), v.
   t. [imp. & p. p. Americanizer; p. pr. & vb. n.
   Americanizing.]
   To render American; to assimilate to the Americans in
   customs, ideas, etc.; to stamp with American characteristics.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Americanize
    v 1: make American in character; "The year in the US has
         completely Americanized him" [syn: Americanize,
         Americanise]
    2: become American in character; "After a year in Iowa, he has
       totally Americanized" [syn: Americanize, Americanise]