A) Since that's obviously NOT happening, (i.e. an area the size of the state of TX is NOT under intense farming just to feed the dogs and cats of the USA) you need to question the initial results that prompted the article. A study by architects, of an agricultural problem. It's easy for a few inaccurate base assumptions to multiply through the calculation chain.
B) That also presumes, I imagine, that the architects drew on their vast repository of knowledge of what goes into petfood, and extrapolated that into prime cuts of beef and lamb. The truth is that the majority of the meat that goes into petfood is the trimmings from the beautiful prime cuts that we hunt down in their styrofoam trays in supermarkets, so while meat processors may be being a bit more generous with their trimmings, it hardly adds up to the huge foodprint (which BTW is of my coinage, thank you Wired mag!) that's being claimed. If the trimmings weren't economically attractive as pet food, unscrupulous operators would find a way to recycle them as stock feed, leading to BSE, scrapie, and human Jakobs-Kreuzfeldt.
C) A lot more pet meat is supplied from culling operations. When hunters cull donkey or kangaroo numbers, that doesn't represent animals that were specifically grown to feed the ravenous pet food market, that represents a lessening of the demand on natural resources that our own meat livestock can then use. So again, there's a HUGE chunk of the pet foodprint that's proven to be actually beneficial.
D) The energy needs of the USA and the foodprint of pets are not equivalent. It's apples and oranges. I can, at need, change my pets to rabbits and chickens, and therefore gain a local food source. The same can't be said of electricity generated by a national grid. Also - I can easily change my pets over to a local food source, such as breeding rabbits and chickens to feed my cat. It would mean I have to expand my garden a bit, and find a local water source - but it's do-able, by me, without too much material needed. Solar panels on the other hand, are beyond my capabilities to manufacture. And that leads to -
E) The amount of land that needs to be covered in solar energy recovery technology isn't the whole story. If you add in the manufacture costs of the solar panels and collectors themselves, you find that the space they cover is the least of your worries... The toxins and pollution and raw materials needed eclipse the environmental effect of the land they would cover.
My readers know that I do everything in my power to be eco-friendly and save on everything and anything that I can. You know that I write pretty impassioned articles myself, pointing out where we're wasteful or messy or just plain malicious to the earth. But crap quality reporting like this, seeking a cheap sensationalist hook, just dilute the good articles.
Yes, your pets are expensive to keep. But it's also been proven that people with pets are less stressed, leading to more productive lives. More productive lives leads to better utilisation of resources, meaning you yourself don't need to use the services of a psychiatrist as often, you won't be at the doctor and consuming medications as much for stress-related illnesses, and you'll produce more in return for the food that you eat than someone who spends a month every year at home sick with SRI.
And you can switch your pet from extensivley processed and packaged pet food (which they don't really appreciate any more than raw feed) to something less processed. My two cats eat frozen kangaroo meat cubes, a small amount of tinned or pouch-sealed commercial cat food, mainly because I don't always have the 'roo meat to hand, and a handful of cat biscuits a week for dental health.
Compare and contrast my cats' one or two tins of catfood a week, one cupful of cat biscuits, and about four cupfuls of diced 'roo, against two almost identical cats eating seven tins of cat food, almost a full 1kg packet of cat biscuits, and no raw meat whatsoever. On top of that, because I keep rabbits and don't overfeed the cats, they also help themselves to the occasional mouse snack when any mice get among the rabbit feed.
Oh - and as far as "feeding America's energy needs" is concerned. Has it ever occurred to these plonkers that one might, you know, reduce one's energy needs instead?