The US has, of course made great advances since the 1950s, especially in the fields of civil rights and equality of the sexes. But what, if anything, has America lost?
The Vietnam war.
Restraint
Off the top of my head some military bases in Germany that were no longer needed after the end of the cold war.
Civility; style; the social contract; the phenomenon of neighborhoods; effective coalition government; effective organized labor; most all passenger rail service; the sense that every adult male is obligated to perform militarily; great hulking gobs of racism and sexism (though large parts remain here and there); polio; roller derby; non-ironic hat-wearing.
We’ve lost quite a few Ryder Cups and the America’s Cup, too. 
Can you be more specific about what things you are thinking about? We surely have lost our dominance in the world markets that we had right after WWII, when most of the other industrialized nations had been bombed to smitherines. That was a tremendous advantage, and one that I think is lost on a lot of people today who think we can somehow reclaim the days of high wage, relatively low skilled factory jobs. We were pretty much the only game in town for about a decade or two after WWII.
I disagree. If you’d asked someone in 1955 what he/she thought they’d “lost” since the 1900s, they would have told you that kids are less polite these days, folks don’t have the same sense of community, ettiquette has tumbled into shambles, and things have basically gone to hell in a handbasket.
Nostalgia is fun, but there never was a time when politicians were honest, everyone was a boy or girl scout, and family values reigned supreme.
Again, I have to disagree. Pastel colored appliances. Fins on massive, ugly cars. The terrible fashions.
There never was one, or, if it was, they forgot to have everyone in America sign it. There were plenty of “deviants” running around-- like in most eras, morality remained mostly on the surface. Peyton Place resonated for a reason.
Which was actually a relatively new phenomenon. The suburbs came into being around the 50s . . . and were harshly condemned by many critics who saw them as stifling and bland. (Levittown, anyone?)
With the suburbs being a recent development, there was not a “strong sense of community” in the way that is envisioned. These people were strangers, after all. You don’t get instant small-town-America when a neighborhood is hastily constructed.
Remember that the idea of “nuclear” families was a relatively new concept. The idea of a couple leaving their home to go out and make a new one was a bit different than what previous generations had done-- families used to stay together, with generations living under the same roof. Perhaps folks from that time would look at the young families of the 50s and bemoan the fact that grandma 'n grandpa (not to mention Maiden Aunt Betsy) were not welcome to live with their children the way they were in the past.
smothers grin
Isn’t that an oxymoron? 
I’m with you on this one. This is something truly to be mourned.
I don’t think that a lot of people had that sense. Hell, I know a great many men who were adult at that time who did not serve, and aren’t bothered a bit by it.
I think that we will bear the mark of Cain for a few more generations because of it, too.
It’s coming back! I see more women wearing hats . . . hope springs eternal!
Its freakin’ mind, apparently.
I think we can safely say that most of America has lost local media. In most major cities, the local TV, newspaper, and radio outlets are owned by giant companies with few ties to the community.
Things it is good that we (and much of the rest of the world) have lost:
Polio, measles, mumps, diptheria, smallpox, whooping cough.
Institutionalized segregation. Stereotyped roles for women and men. (Remember when want ads had “help wanted – female” and “help wanted – male” sections?)
Things it is sad that (some of us) have lost: Stars. In much of the country, when you look up in the sky at night, you see only a handful of the brightest stars; the rest have been lost in the glare of artificial light. Where I live, the night sky isn’t even dark; it’s pink from the glow of the neon signs of the hotels near the interstate highway interchange a mile or so away.
The US has lost much of the moral authority/stature it had with the rest of the world during & right after World War II.
the concept that individuals are responsible for their actions.
I have to agree with you here - I would say the US has lost the respect of other nations. It seems that in the past, the world looked to the US for guidance almost… now it’s more “off they go again, what are they saying now?” :rolleyes:
Horseshit. We have a larger proportion of our population incarcerated than any other country. That’s not what you would expect of a society that blames society. See this thread: http://boards.straightdope.com/sdmb/showthread.php?t=304071
Segregation,and naivety in fighting wars and installing regimes, but not all of it. Its main rival, Communism.
International prestige, but that couldn’t really be avoided. In the 50’s, if you didn’t like the Soviet Union, you pretty much had to look up to us because economically and militarily we were the only country capable of competing with the Soviets. But now both the EU and China have power comparable to the United States, so nobody has to step lightly and pretend to like us anymore. As tempting as it is to blame the whole thing on Dubya, it’s really the logical result of worldwide economic growth.
Didn’t we used to have a Constitution and a Bill of Rights and stuff?
Ah, what the hell, nobody really misses them!
respect.
Yet more hystericalness on your part BrainGlutton.