Innocents at Home : BACK HOME A Foreign Correspondent Rediscovers America <i> by Mort Rosenblum (William Morrow: $19.95; 447 pp.; 0-688-07780-3)</i> : THE LOST CONTINENT Travels in Small-Town America <i> by Bill Bryson (Harper & Row: $19.95; 283 pp.; 0-06-016158-2) </i>

Like the proverbial vacation slide shows inflicted on polite dinner guests, travel books run the peculiar danger of tedium in recounting minor adventures and mishaps that may excite an author but are capable of putting the reader to sleep. These two books by Americans--come home after years abroad to take the nation’s pulse--hold our attention with clever, grabby prose but fail to cover much new terrain.

Both are written by gifted American journalists; Mort Rosenblum, author of “Back Home,” is a Paris-based correspondent for the Associated Press, and Bill Bryson, author of “The Lost Continent,” is a humor and travel writer who lives in Yorkshire, England. The books have much in common. Both men wander the Lower 48 alone, searching for America’s soul, trying to find (and read) meaning into old motels and chance encounters with policemen, waitresses and store clerks. Bryson sets out from his hometown of Des Moines, Iowa, in an aging Chevy Chevette, on loan from his mother, looking for what he terms “the perfect town.” Rosenblum travels mostly by rental car, starting his multilegged journey in New York City, which he playfully dubs “The Big Fruit.”

Both visit Gatlinburg, Tenn., and are appalled by its crass commercialism and tacky kitsch. Both savor Savannah, Ga., where the downtown, “frozen in a perpetual 1959,” says Bryson, remains a desirable place to live. Both tour the Deep South only to come away with the startling conclusion that--hold onto your hats--racial prejudice has not yet vanished. What’s more, each man seeks out the tourist traps, as if to plumb the depths of the American character one must first pay homage to its celebrity icons. We see Elvis Presley’s boyhood home in Tupelo, Miss.; Mark Twain’s boyhood home in Hannibal, Mo., and Dolly Parton’s Dollywood Amusement Park in Pigeon Forge, Tenn.

Rosenblum is the more serious of the two writers, attempting to follow in the footsteps of Alexis de Tocqueville and produce a commentary on the state of the nation in the late 1980s. The resulting book is a lively montage, into which the author laces original reportage, travelogue whimsy and information from sources as disparate as the Department of Defense and Spy magazine, along with ruminations on what ails America. Along the way, he picks the brains of family and friends, like the M.I.T. sociologist who is also his cousin’s husband, and fellow journalists from around the world, now returned home.

“America is no longer a melting pot,” writes Rosenblum. “It is a stir-fry wok. Whatever new ingredients are added to the rest, each retains its particular flavor and shape. But a certain uniformity is cooked in, giving us common characteristics, standards and frames of reference.”

Rosenblum’s own frame of reference is that of ‘60s-vintage liberal who, returning for his first serious visit after a two-decade absence, seems startled at the country’s failures and often disappointed that things are no longer as they were--or as they are now in France or the 145 foreign countries from which he has filed dispatches. Rosenblum takes note of, and takes on, such betes noires as the reign of “corporate martial law” in America, the ruling principle of greed on Wall Street, white poverty in Appalachia and our growing dependence on illegal drugs. But on his wide canvas, he seems determined to paint only gloomy shades.

His perceptions run the gamut from the trenchant to the hackneyed. “The only phrase in America heard more often than ‘Have a nice day,’ is ‘the bottom line,’ ” he writes, in an example of the latter. After the fashion of H. L. Mencken, Rosenblum relishes his role as curmudgeon (and even calls himself one), using the book as a forum to sound off on pet peeves, such as the anti-smoking campaign that has gripped America. He appears seriously troubled by the emergence of what he terms “health fascists,” and, like a debater championing a losing cause, summons up dubious studies that would seem to dispute the dangers of passive smoking.

Indeed, even his visit to the Arizona Daily Star--his old paper in his hometown of Tucson--proves to be a “sobering” experience. “I had left a smoky newsroom of clattering black typewriters, where a battered old-timer from Chicago sneaked hits from a bottle of Jim Beam in the darkroom. I came back to a carpeted salon of eerie green computer screens and respectful young reporters nibbling trail mix. . . . The trash barrels that had smoldered when confused with ashtrays all were lined in clear plastic Baggies. There were no ashtrays at all. Funny world. In a newsroom in Warsaw you could not write what you wanted. But you could smoke a cigarette.”

It would appear that Rosenblum’s objectivity has been stricken by an acute case of nostalgia. While railing against the scrub-nosed reporters who are in it for the paycheck--not the glory, as in the good old days, by gum--Rosenblum fails to consider the underlying conditions for these changes. The standard of living for the young has declined since the late ‘60s. Money is tighter; a paycheck must stretch farther. And, could our health consciousness be born of the declining health of the planet? He doesn’t make the connection.

Rosenblum is at his best when he arrives at a new place with an open mind and allows himself to be vulnerable. In one especially moving encounter, he strikes up an acquaintance with a Pennsylvania Dutch man, who confides his distaste for being on constant display. “Saying good-bye, I asked Mike if I could photograph him with his daughter,” he writes. “He looked pained, caught between courtesy and disapproval of yet another jerk with a camera. ‘You can take it from across the road, but I won’t pose for you,’ he said. I apologized for even suggesting it. And I wished I were dead.” What works here is that Rosenblum has joined hands with the Americans he’s analyzing. No longer the foreign correspondent from on high, he admits to wanting what they want, which is a slice of the past in a world overdosed on change.

Bill Bryson’s “The Lost Continent: Travels in Small-Town America” bears no relation to the sort of thoughtful travel writing that was so masterfully rendered earlier this year by V.S. Naipaul in his book, “A Turn in the South.” To say Bryson has explored America’s small towns is like equating the character development of “The Beverly Hillbillies” with “The Sound and the Fury.”

Though Bryson uses a search for the perfect small town as a pretext for his “travels,” in fact, his book is merely a forum for the put-down humor so popular these days--sometimes funny, often adolescent. Usually he picks on sitting-duck targets.

“K-Marts are always full of the sort of people who give their children names that rhyme: Lonnie, Donnie, Ronnie, Connie, Bonnie. . . . Every woman there has at least four children and they all look as if they have been fathered by a different man. The woman always weighs 250 pounds. She is always walloping a child and bawling, ‘If you don’t behave, Ronnie, I’m not gonna bring you back here no more!’ ”

He takes on the Southern accent. “The average Southerner has speech patterns of someone slipping in and out of consciousness. I can change my shoes and socks faster than most people in Mississippi can speak a sentence. Living there would drive me crazy. Slowly.” He calls Iowa “a dump.” Of Missouri, the “Show Me State,” Bryson wonders if they didn’t really mean: “Show Me the Way to Any Other State.”

Yes, there’s something funny in this put-down humor, but there’s also something amiss: a detachment and dehumanization that fails to reach beyond stereotype. Bryson ever gets out of his car. The few times he does, he never interacts with anyone. The people he encounters are invariably dim-witted, 250-pound foils, walking opportunities to demonstrate his facility with the one-liner potshot.

No doubt there is much to bemoan and much to ridicule on the American landscape. But, for my money, I’d rather see some digging--even in line at K-Mart.