What is the best motorcycle for traveling across the US?

The three Japs produce rather nice touring cruisers that would suit you just fine:

Suzuki Boulevard C50T, Yamaha V Star 950 Tourer, Kawasaki Vulcan 900 Classic LT, and the lilttle Honda Shadow Aero VT750C (after you add saddlebags and a windshield.)

I'm partial to Kawasakis, but for your situation I'd consider an '84-86 1200cc Gold Wing or preferably a '86-05 Kawasaki ZG 1200 Voyager.

The GWs are good bikes and for their age, parts are still fairly accessible. They are reasonably priced, smooth, quiet with stock exhaust, comfortable, have a low center of gravity and have plenty of storage space should you want to take along the kitchen sink. However, the notorious alternator failure can be a $1500-$2000 repair and requires removing the engine. Should that happen on a trip, that would sure take the fun out of it and make the trip expensive. The later GW 1500 and 1800 6 cylinders are wonderful bikes but are much bigger, heavier and more expensive. And on the 1800, there's a lot of expensive plastic bodywork that can be busted should you dump it.

The ZG 1200 is a good, dependable bike. While there are lots of '86s, personally I'd steer clear of them for two reasons. They had an igniter-starter chain problem which "should" have been fixed years ago under warranty, but to be sure that requires comparing igniter ID#s. Also, the '87 and later fairings had an extra lip on the fairing that greatly improved wind protection. Electronic cruise control was also available on the '87 and up, but not the '86. The Voyager XII (as they're called) are actually quite lightweight compared to other full dress touring bikes. They made them more or less unchanged for 19 years, meaning they were less expensive when new, are less expensive now and dealers still stock all kinds of parts for them no matter where you go. It doesn't matter whether you have a 5 year old or a 24 year old XII, the same part will fit. They have lots of luggage space, good stereo and get great gas mileage, often as good as bikes with half the displacement. About the only problem is that some people report the front wheel wanting to wiggle a bit when riding. This seems to vary from bike to bike and person to person and is probably a combination of tire make and wear, road surface, suspension loading, bearing wear and so on. It's not something dangerous, just noticable to some people.

For $3,500-$4,500, you can get a good XII that you could gas up and ride across country without any worries. That's about the same as what an '84-86 GW would cost but the part situation is completely different. I ride an '84 Voyager XIII (a totally different bike) and I carry vital spare parts with me when I travel out of state. Not the most comforting feeling I must say.

Any of the touring bikes, will do. While a Harley, is the best choice for major long miles. A Honda Goldwing, is a better bike for a newer rider.

Riding across the country, is not a trip to take lightly. It's also not as cheap, as you may think. Oh it's not to bad, if you camp out. Unpacking and repacking a motorcycle, can be a pain in the ***. Depending, on how much you want to ruff it. In 1983, I rode from South Carolina, back home to Wisconsin, the long way though California. I only had my gear, from the Army and a pair of tarps. I spent most nights, under a tarp. Tied to some trees, draped over the bike, then staked to the ground. A picnic table, if the rest stop had no trees. Most rest stops, are a good place to spend the night. I was 20 at the time, with a months leave from the Army.

Spending a night in a motel, however can add up. Even camp grounds, are getting expensive.

I would buy the motorcycle. For the price you are in the range of a suzuki boulivard s40. The thing about travel is there is always something to see right where you are. I used to live in Cawker City Kansas. They have the largest ball of twine. If you lived in Milwaki you could use your motorcycle to see the breweries. If you lived in Southern California you could use your bike to see the giant redwoods. No matter where you live there is something within range of a days travel to see. And personally, a day on the motorcycle to get there is far more memerable than 12 hours on a crowded plane. With all the security today air travel is just not worth it anymore. With a motorcycle you can get up in the morning have breakfast, decide that you want to ride. If you buy the Suzuki mentioned you will get 63 MPG there and back and if you have some extra money you can buy a hotel room and see the sights whereever.

Goldwings and equivalent Harleys are insanely expensive unless you plan on doing a lot of touring and little else they are not much fun for simple commutes. And cost a small fortune for major servicing.

I would look at BMW R1100 and 1200s, Triumph Sprints, Honda VFR750s (they seem to be praised over the 800), Honda ST1100 (Pan-European).

However I would not recommend any of these to a beginner.

For that I would suggest after a series of training and some experience of riding on the road, an SV650, Bandit 600, Fazer 600, ER6n perhaps.

Not sure how much money you have, or your plans for said-motorcycle after the trip is over. Buying a bike for a specific trip isn't long-range planning, no pun intended. Be that as it may, the answer is probably "whatever appeals to you most." Motorcycles are more about the heart than head, in the end. There are dozens of possible specific answers, most of which are "opinions" with no relation to what turns YOU on.

I've gave some thought to what bike I'd choose to do exactly what you want to do and decided that if you're traveling alone I'd look into some of the sport tourers that are out there. They have plenty of power, fairings for protection, a comfortable riding position, less weight than a full dresser thus easier to ride and maneuver, and enough storage for one person's gear. I've noticed that all the really serious iron butt competitors choose this type of bike for the long haul. They do it for a reason.

Take a riding course and learn to ride the correct way. The Motorcycle Safety Foundation (MSF) offers classes. They provide the bike. Look them up on line and find a class near you. A Harley Road King or Harley Electra Glide would be my suggestion. You may want to consider a used one to save some bucks.

The key word is "beginner". Beginners have no business riding 1800cc land yachts. The Honda Deaville NT700 and the BMW F800ST would be good machines for you. Or the Suzuki V-Strom 650, once you add some panniers.

Love those already posted suggestions...about exhaust, and models to consider. (If it is too loud, you won't like it, and you will fatigue faster, get headaches, etc.) Look for an old Goldwing, or Aspencade, for your first trip...in case you 'damage' it. But do take that time to learn to ride it properly...and make sure that you can handle the weight of the bike as well. Ride safely.