Bang. "You're OK, keep driving," my wife says firmly above the sound of smashing glass.
We are driving a 7.6-metre Cruise America RV on the wrong side of the road through the mountain passes of the spectacular Yosemite National Park and a large boulder has just taken off our side mirror.
We expected some damage to our "monster truck" on our ambitious 80-day family adventure, starting in Los Angeles and driving a lap of the United States - but not after just three days.
It had started so well. We had bounced from a baseball game at LA's Dodger Stadium to "the happiest place on Earth" - Disneyland.
Our children, Amelie, 11, and Jack, 5, go on the Splash Mountain ride four times and we earn big parent brownie points.
The US is like one big Disneyland, with ubiquitous attractions and a constant sense of deja vu thanks to film and television.
In LA, we visited the Hollywood sign, rode bikes along Santa Monica Boulevard and stood where Route 66 starts (or ends).
We cruise out of Yosemite through Tioga Pass, which is above 3000 metres, and stop for a summer snow fight. A few hours later, we are below sea level in Death Valley, where it is north of 40 degrees. The heat is oppressive and made worse when I plug the RV sewage outlet to the wrong pipe.
Death Valley is a pit stop to the world's biggest erosion example - the Grand Canyon. At 1.6 kilometres deep and 29 kilometres wide, it tops the wow factor scale. We ride bikes along the rim, trying to spot a massive condor; the vulture is the largest bird in the US.
Our next stop had more vultures: Vegas, baby.
We grab a magic show, where the kids enjoy seeing their dad pulled on to the stage and, of course, we have a little bet.
We then head east to the Rocky Mountains and one of the United States' coolest cities, Boulder, Colorado. It is the peak of summer and bands are playing in the main street. Nearby, people are dancing with hula-hoops at a silent disco - no surprise here, Colorado was the first state to legalise cannabis.
Out of the mountains and it is a big drive to anywhere, but there are cheerful distractions such as camping at the small town of Paxico, Kansas (complete with tornado shelter) and stopping at the Wizard of Oz museum in Wamego. Yes, Dorothy, we're in Kansas.
Out of the Great Plains, we are soon dancing to country music in Nashville, living the Elvis experience in Graceland, Memphis, and visiting the Lorraine hotel where Martin Luther King jnr was assassinated.
We follow the Mississippi river south, stopping to hook catfish with the locals before hitting the Paris Quarter and some trumpet-heavy jazz in New Orleans.
On our sweat-dripping Louisiana swamp tour, we feed giant marshmallows to the 'gators and racoons, as the boat captain notes in a thick Creole accent "everything eats everything out here".
We make it all the way to the Florida Keys before things go a little pear-shaped and we have our first family meltdown. A beach stop quickly cools everyone down.
We stop by Florida's Kennedy Space Centre to have lunch with an astronaut and see where Apollo 11 left for the moon. The kids are more interested in the next stop, the Wizarding World of Harry Potter in Orlando, with the finest butter beer and broomstick ride around.
Next, we head up the east coast and visit an antebellum plantation and the southern belles, Savannah and Charleston, where Spanish moss hangs from the trees as though it is still the 1800s. The historic cities link to the south's hidden gems, its beaches.
We hit North Carolina's Outer Banks - a sliver of connected sand islands popular with pirates in the 18th century. Ocracoke Island is the sort of place where you could catch your breath for a year or two and drift like a beachcomber.
The wide windy beaches are also where the Wright Brothers took their first flight at Kitty Hawk.
At Fish Heads bar and grill, a grungy hangout on a Rodanthe fishing pier, we eat shrimp by the bucket and drink to the sunset while we watch families light fires on the beach ready for their summer beach parties.
We cruise to Washington and take in the Fourth of July fireworks with good friends and skip over to Gettysburg to catch the annual battle re-enactment.
Time to ditch the RV for a while and jump on mopeds to explore Pennsylvania's Amish country.
Then it is a train from Long Island to New York to visit the Statue of Liberty and play "Where's Wally" on the red steps in Times Square.
We eat lobster in Maine and get soaked at Niagara Falls before heading west to the Little Bighorn battle site in Montana where Custer fell to the Sioux warriors and on to Cody, a cowboy town founded by Buffalo Bill with a brilliant summer night rodeo, where the kids get bucked on a mechanical bull.
Mount Rushmore's bulging presidential heads are impressive; the nearby and unfinished 170-metre-high Crazy Horse sculpture even more so. The north-west is full of fantastic national parks and we want to seem them all.
There is a reason they call it the Badlands: the landscape looks apocalyptic and there are plenty of rattlesnake warning signs.
Yellowstone, the oldest and most touristy of the national parks, is more inviting. We discover the Old Faithful geyser is desperately in need of some Viagra, while the deep blue thermal pools and wandering bison are impressive. Better is to come: the Grand Teton and Glacier national parks.
The nature river raft drift at Grand Teton with bald eagles perched above, beavers diving into the river and moose grazing on the banks would make David Attenborough take a break.
We take a hike and, to keep Jack interested, we sing "we're going on a bear hunt". Bingo. We come across a large black bear scavenging 10 metres away.
Amelie starts reciting the "what to do if you see a bear" rules and scolds us for not buying the $50 bear spray. As I quickly take a snap, the bear comes much closer. "Don't run" they say, but try taking that advice.
A few kilometres up the road and straddling the Canadian border is Glacier National Park, boasting one of the world's most scenic drives, the Going-to-the-Sun Road, a windy 50-kilometre mountain drive with stunning/terrifying cliff drops metres away. My increasing confidence in the RV does not extend this far - we take the park shuttle.
The view from the Village Inn of breathtaking Lake McDonald is unforgettable. Looking from the verandah across the lake to the snowcapped mountains, it hits us - after 20,000 kilometres, we are totally relaxed.
And we still have one side mirror on the RV and the west coast to go.
Some might think three months in an RV with a family of four would be claustrophobic. But when the mountains, rivers, lakes and beaches of the US are your lounge room, it feels like a mansion.
usa.gov/Citizen/Topics/Travel-Tourism/State-Tourism.shtml.
The Lonely Planet USA and Discover USA's Best National Parks guides are very helpful.
Qantas operates direct daily A380 services from Sydney and Melbourne to Los Angeles. It also has daily B747 services from Sydney to New York, via Los Angeles, with daily connections from Melbourne. Qantas also flies direct Sydney to Dallas/Fort Worth with six services a week and daily connections from Melbourne.
For more information, see qantas.com.au or call 13 13 13.
Virgin Australia has daily flights to Los Angeles from Brisbane and Sydney. See virginaustralia.com.
Australians citizens can apply online for a tourist visa for up to 90 days to visit the US at canberra.usembassy.gov/nonimmigrant-visas.html.
We hired our Cruise America RV through Flight Centre (see flightcentre.com.au). You can also book direct through cruiseamerica.com. If you are planning a long trip, look for unlimited miles. (We broke the record with more than 23,000 kilometres.) It is also worth considering travel insurance to cover the excess, which can be as much as $1000.
For hot showers, Wi-Fi and pancake breakfasts, we stayed at KOA campgrounds (see koa.com) or Good Sam campgrounds (see goodsamclub.com/travel/campgroundsandrvparks.
For the best scenery, the authentic camping experience and a cheaper rate, head to the state parks and national parks. Bookings are essential in peak season. See nps.gov/findapark.
Gettysburg re-enactment, July 3 to 5. See gettysburgreenactment.com.
Cody Stampede Rodeo, June 1 to August 31. See codystampederodeo.com.
Oklahoma Joe's Kansas City Bar-B-Que. You have not eaten ribs until you have eaten there. See oklahomajoesbbq.com.
Maine lobster in Bar Harbour. They sell lobster like Australians sell meat pies. Sit down to a whole lobster for $20.
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