IN THE FIRST DOG DAYS of this sultry new decade, two films of precious little artistic merit and perhaps less social value have burst on the scene to entice us into the cool, dark air of the neighborhood cinema. These are movies about jes' plain folk who might live around the corner or across the state, silly stories of ordinary people who want to be rich so that they can be happy, happy in the American way.

Strangely enough, it is this slapdash indictment of the American system that differentiates these first "summer" films of the eighties from movies of other summers. Neither of these films has a political consciousness to speak of, and both are only mildly--and spottily--entertaining. But each takes a stab at the American capitalist system and the Protestant ethic of hard work and honesty. And in each film, the American way of life takes a beating, handily defeated by chicanery, theft and vice.

Jane Curtin, Jessica Lange and Susan St. James play three women down to their last nickels and thyme in High Cost of Living, each eager to drop the bad script life has tossed them, all of them desperate for money. They decide to rob a shopping mall. Curtin, with her wing-nut mouth, bolting eyebrows and thunderous thighs has the biggest role. While she never slips into Mrs. Loopner, or any other of her Saturday Night Live characters, Curtin is not as successful on the silver screen as she has been on the tube.

This is largely true of Lange and St. James as well and might be attributed to the earnest but flat script. While Lange purrs as beautifully as a Persian cat and St. James creates a perfect suburban mother, the trio never manages to build the kind of fast-talking, silly camraderie maintained even by Charlie's Angels.

High Cost of Living has no value, of course, on a practical level but director Scheerer cannot be accused of not trying. Except for the outlandishness of the robbery plot, his portrait of three middle-aged middle-class women in Eugene, Oregon is devastatingly accurate. Their adventures with the police, with gas station attendants, exhusbands, husbands, and little leaguers have the all too humid air of authenticity about them.

The very choice of a shopping mall as the target of their heist attempt makes an air-conditioned, claustrophobic comment about the American middle-class. Never mind that if these women sold off even half their wardrobes, they could drive gas-guzzling American cars for years--the cost of living is not only expensive, it is high. And part of that high cost is the material drain of today's values. Curtin, Lange and St. James each play women who would have no trouble voting for Ronald Reagan in November if there were to be a sequel called, say, How to Make American Great Again. But they are also citizens who, unless reminded, would not vote at all. With its stumbling but accurate portrait of America caught in the throes of a mid-life crisis, this bubbly comedy provides more chills than laughs.

USED CARS attempts a similar brand of semi-political humor where all the "statements" are cheap shots at American institutions, including Jimmy Carter. It stars Kurt Russell, the notorious Elvis impersonator, as a stupendous used car salesman anxious to make the grade as a U.S. Senator. Young Kurt is positive that with enough fast-talking, and with his charming good looks, he can fool all of the people all of the time, despite his plaid sport jackets and polyester slacks.

This knee-slapper details the rivalry between two used-car-selling brothers (both played by Jack Warden) and the shenanigans they perpetrate to dominate the used car market in this small Southern California town. Due--understandably if you've seen How to Beat the High Cost of Living--to a slow economy, business is bad in both lots, which face off across a strip of pavement that serves as a demilitarized zone. Soon these good ol'boys are playing at war, and their tactics become increasingly destructive.

Whatever political comment Used Cars aims to make (and there is a hilarious moment involving a presidential address), it gets lost in the car race that consumes the second half of the film. All of it is tongue-in-cheek, silly with a hint of satire but the slam-bang plot turns the movie into a predictable demolition derby.

Only one line stands out. As Russell leads a caravan of 250 used cars across the California desert, he realizes that he'll never make his deadline if he sticks to the speed limit. Turning and speaking through a megaphone to the high-school students driving his pack of cars, he prepares the kids for a history lesson. "This is how we used to drive," he yells, "at 75 miles per hour!"