The Tavern, 5 Royal Well Place, Cheltenham (01242 221212). Meal for two, including drinks and service: £90

This is a tale of two restaurants. One knocks out platefuls of pleasingly sturdy food, singing songs from sun-kissed Mediterranean shores. The other does not. Both, to be fair, have the same cheery, efficient service provided by a bunch of lads who are young enough to get up late so as to show you a good time come evening. Then again they would share this, for these two restaurants are one and the same. The Tavern in Cheltenham has one kitchen knocking out food which is by turns both lovely and dispiriting. It's baffling.

This is not my first time in the building. I last reviewed here in 2009 when, known as the Royal Well Tavern, it served solid French bistro classics. It did a proper bit of coq au vin. It also didn't pretend to be anything other than a pub. There were narrow pew-like benches, upon which my arse only just perched. Now it's had a major makeover and mislaid its royalist commitments.

There are plump leather-bound banquettes and gnarly bits of varnished wood for tables. It's all low lights and clutter, and menus printed on brown package paper in a typewriter font, an immediate reminder of the artful artlessness of Spuntino in London, which doesn't feel accidental. By the door there is a pair of DJ decks. Oh God. There may be dancing. The message is clear: this is a young people's restaurant and on a Saturday night it's packed with them.

What they make of the fusty "second home in Tuscany" options I can't imagine, but that food is very good. There is a starter of sweet-salty clams amid a stew of borlotti beans and chorizo that has us sucking at the shells. There is a whole roast partridge on a mess of creamy polenta studded with butter-seared ceps, with a little sticky jus to keep everything moving. At the end there is a cast-iron pan of black and purple grilled figs tumbling apart, with dollops of cream, walnuts and dribbles of sticky honey. So far, so bargain-basement River Café.

But this is not where the Tavern's heart or the rest of its long, complicated menu lies. Its menu is driving into the sunset in a vintage Caddy, all chromium trim and fin. It's very much mid-Atlantic twang and Brooklyn (by way of London) cool. It is a me-too exercise in Dirty Americana. Think wings and sliders, pulled pork and shocking things done involving heat and cheap cheese. There's nothing wrong with any of that; this food, done right and sold at the right price, can be an intense pleasure for which guilt is eagerly deferred. Here it is not done right.

It starts with a French dip, the classic diner sandwich of sliced roast beef in a soft bun with a bowl of beef gravy on the side, for dipping into. It's a blunt instrument, a meeting place for hot soft meat and sticky meat juices. Here the meat is dry, the sauce is over sweet, the plastic molten cheese unnecessary and the £10 price tag indefensible. Let's be clear: the real thing, invented in Los Angeles, ain't exactly a work of art. But it does have its virtues, one of which is lusciousness. At the Tavern it has been misunderstood, as if American wasn't so much a different accent as a different language altogether.

A devilled scotch egg for £4 brings something with a dry solid yolk and a sausage meat casing sent to the dark side solely by the blunt addition of what tastes like cayenne pepper. Devilled or hellish? It's not a tough call. The cob salad arrives in a jar, the lid screwed on tight. There are lumps of cold egg, dry chicken, boulders of blue cheese, a few bacon bits and a couple of leaves. If there's any dressing it is doing its best not to catch my eye. It isn't a salad: it's a salad filling dreaming of two floppy bits of Mothers Pride in which to hide.

We order the collard greens. This is not an attempt to eat healthily, for collard greens aren't healthy. The American food writer Paula Dean, the queen of trash food dressed up as southern hospitality – she once deep fried cheesecake – also does a recipe for collard greens. It takes two hours of boiling and involves half a pound of smoked meats to each bunch of greens. What the Tavern delivered was some meatless, garlic-tossed cabbage. It was collard greens seemingly made by someone who has never eaten them.

Worse than this was the special which, we were told breathlessly, was part of a competition in the kitchen. A different member of the brigade was invited in rotation to come up with something to be sold under the heading 'Fun in a bun'. Tonight's contestant lost by offering pulled pork with deep-fried macaroni cheese, plus homemade cheese and onion crisps. Fun in a bun? I've had more fun having my verrucas removed. The pulled pork was actually rather good. Too often it's overcooked and slathered in a dreary sweet sauce that kills both the flavour and your pancreas. This was proper porky, but you had to prise it away from its unsuitable company to discover this.

Breaded and deep-fried macaroni cheese is not a topping. It's a warning in a government health information film. It's the ghost of Elvis Presley on the bog, trousers round his ankles, expelling his last. It's horrid. And why would you attempt to make your own cheese and onion crisps when Kettle Chips will always do it better than you? The bun was also burnt.

The one bit of the American food menu we tried that was worth the visit (if not the £7 price tag) was the dirty mac 'n' cheese, with the kick of jalapeno chillies and a good crisp crust. Admittedly the menu is long and there may be other such gems to be mined, but it's not as if we didn't put our backs into ordering. And then they fired up the decks, put on Daft Punk and I began to feel very old indeed.

There used to be a cartoon stuck to the wall of this newspaper's offices, mocking the deadening effects of the pedantic subeditor. The sub is leaning over the shoulder of a Victorian chap who is scribbling away with a quill. "Come, come Mr Dickens," the sub is saying, "it cannot be both the best and the worst of times." At the Tavern in Cheltenham it really can.

Jay's news bites

■ It's unfashionable to big up chain restaurants. But, hell, I gave up being fashionable decades ago, so: for pulled pork, ribs and wings, the small Bodean's chain in London's Soho, Clapham, Fulham and Tower Hill, does a great job. Its long-smoked beef short ribs – half a slab for £20, enough to feed two cavemen – are the stuff of joyous meat sweats. bodeansbbq.co.uk

■ Where your meat comes from matters. If you want to know more, get the new cookbook from The Meat Crusade, the campaign to support local high-street butchers and to educate consumers on the business of quality meat production. It's launched today at Countryside Live, on the Yorkshire Agricultural Showground. meatcrusade.co.uk

■ In a move that is quietly terrifying the online supermarkets, Amazon has started selling food. The emphasis so far appears to be on dry stores, but it also offers items that you definitely can't get from Ocado, including a range of astronaut food, as used by Nasa. Mmm! Freeze-dried Neopolitan ice cream, yours for just £4.90.

Email Jay at jay.rayner@observer.co.uk or visit theguardian.com/profile/jayrayner for all his reviews in one place. Follow Jay on Twitter @jayrayner1