THE LAST MARRIED COUPLE IN AMERICA -- AMC Carrllton, Jenifer, K-B Crystal, K-B Silver, Roth's Randolph, Springfield Mall and state.

A perfectly good comic premise has been thrown away in "The Last Married Couple in America," after having been wrapped up in a style that could be called Suburban Smut.

That theme is the influence of sociological fashion on individuals. George Segal and Natalie Wood play a long-married couple whose friends are all divorcing. As they and their entire set put all their efforts into being trendy, one can imagine that, having married when all their friends were marrying, having produced three (why not 3.5?) children when that was the fashionable number, and having had extramarital affairs when these became common, they would be susceptile to the new rage for breaking up.

Admittedly, it would be difficult to establish sympathy for characters who are that open to suggestion about how to conduct their lives. But this picture has the gumption to suggest that the fault lies not with weakness of character but with a society in which the pressures against marriage are overwelming.

That's where the smut comes in. In the world of this film, a man cannot keep his office door shut against his wife's friends who attack him with obscene propositions. A respectable woman is under constant siege, not only from young tennis bums but from professional men with the courting techniques of rapists. A family with young children finds itself powerless to keep prostitutes and pornographers out of its social life.

According to the title of the film, this must be "America." If so, the story of a family trying to live in it isn't funny.