Among the ideals of equality, liberty, and the pursuit of happiness, the last is quintessentially American. An American devours any idea that promises a chance of greater happiness. If this idea fails, undaunted, he moves on to another. The pursuit of happiness has installed the taste for perpetual design into America's DNA.
Liberty cultivates tolerance, which encourages social experimentation. A degree of equality ensures that no life that one can usefully learn from is wasted.
"Her" can be watched without sound (or alternatively, without visuals). The movie's representation of the near future is loyal to the original. The improvements are in interior, sartorial, and urban designs; the make-up is subtler; the manners are milder; the age is post-advertising and the better for it. The movie is set in the America whose success has ushered a post-American era.
Individuals waste their time with pets. The time spent with an OS would at least cary the promise of personal growth. As flight simulators make better pilots, OS friends would make one better at interacting with humans. The menial aspects of psychotherapists' and child psychologists' jobs would be outsourceable to machines. When with other humans, humans would devote themselves to the art, not the predicament, of human communication.
The casting and acting are impeccable. Amy Adams and Scarlett Johansson develop characters, not personalities. Joaquin Phoenix (Theodore) is careful (and carefully chosen) not to make his character bigger than his intended part. Rooney Mara is skilfully miscast as Theodore's ex-wife.