Check out the Touring forum. http://www.bikeforums.net/forumdisplay.php/47-Touring

Riding across the country self-supported in 30 days is VERY ambitious. You won't have time to do anything but ride your bikes, and you'll be too tired to do much anyway. I would pick a shorter route and give yourself more time to have fun.

I'd recommend the Pacific Coast route (Canada to Mexico)- www.adventurecycling.org has maps, or you can buy the book "Bicycling the Pacific Coast" by Kirkendall & Spring - or you can just keep the ocean on your right. Start in the north and go south to take advantage of prevailing winds. There are tons of hiker/biker camp sites (cheap camping), great scenery, some hills but not too much. You can probably get the whole coast done in 30 days but if you run out of time you can catch a bus, train or hitch-hike. Fly in to Seattle (or connect to Bellingham) and fly out of San Diego or LA. Southwest Airlines has reasonable fees for transporting the bikes, and has a lot of flights between western cities, so if you have to fly out of the same place you fly in to back to Europe, this could help. Alaska and Frontier are also good, United/United Express & Delta are expensive.

Western Express is really really empty in Nevada. I've not ridden it, but I have driven it and would say it's probably not your best choice for first time tourers. Lots of stretches of 80 miles with no services (water, food) and not much traffic to give you a ride if you get into trouble.

Another great thing to do, especially if you are here mid-summer, would be the Great Parks routes (also adventure cycling). Lots of mountains, and a bit more variety than the coast.

Can't tell if you are from here or from France.... in case you are not from the US, notice that the US is very big in the north-south direction, and the time of year you are traveling makes a big difference about where you will find the best weather. If you're here in summer, you don't want to ride in Arizona and New Mexico, it's too hot, but Wyoming and Montana and Colorado are great. And of course, the opposite if it's closer to winter.

Most tourists who are carrying their own gear and camping average 60-65 miles/day. If you are traveling really light and staying in motels, your distance can go up, maybe up as far as 75-85/day, but you get caught up in logistics of finding a hotel, so you may have to have shorter days to make the hotels work, and of course, its more expensive. If you are counting on high mileage, even one missed day (sickness, meet the boy/girl of your dreams, waiting out bad weather, etc) can be a disaster for your schedule, so try to build in a little slack time.