I am from the UK and am spending up to 2 years touring the US and Canada in a Thor Vegas and towing a Jeep Wrangler.
I got a 10 year multiple entry Visa via a visit to the US Embassy in London, and on my first entry at Chicago in June last year was given a 12 months stay. I was advised that if I wanted longer, just leave the country before the year is up and come straight back. I went home for Christmas and got another (concurrent) six months till July, and am going home for a holiday via Vancouver in Canada that month and will seek another six months on my return.
I took good advice and joined Escapees RV Club as well as Good Sam Club before coming to the US. The Escapees RV Club offer a domicile service as well as a mail forwarding facility. I used their domicile address in South Dakota (Box Elder, near Rapid City) as you are allowed, as an alien, to Title a vehicle and pay your sales and vehicle taxes against the domicile address provide by Escapees. The only problem I had was that in order to pay your dues you have to be 'in the system' in S Dakota to make a payment. To be 'in the system' they need you to be recorded against a drivers license number or Social Security number. To get round this they issued me a "Temporary Driving Permit' (at no cost) that gives me my a drivers license number.
I purchased my motorhome via a UK dealer that imports my model. They sold it to me at the American price and arranged for me to collect it from a dealer close to the factory. The dealer performed the pdi and sold me a $5 paper plate in order I could drive the motorhome to South Dakota to register it and pay my sales tax. I realised on arriving here that I could probably got a better deal by speaking direct to a dealer in the US, but that's a different matter!
I purchased my Jeep from a dealer in Rapid City via their web site, eMail, and phone. The dealer took my build requirements, made the factory order and had the Jeep delivered to their showroom ready for my arrival. I paid via an International Bankers Order obtained from my bank the UK. The dealer also recommend a company to supply and fit my Jeeps Blue Ox tow equipment and Brake Buddy, which they had done for me ready for my arrival. They even took the Jeep there with me in convoy with the motorhome so I could be instructed in the attachment and use of the equipment.
Obtain medical insurance before you leave home. Just two months into my adventure I took a fall and spent three weeks on crutches recovering from ligament damage so I have recouped the cost of mine already! There are a number of providers to be found on the internet.
I have had a fantastic time touring the US since last June, and have covered 15,000 miles to date. I most enjoy staying at State Parks where facilities are often basic, and use established campgrounds when I need to. I use Good Sam's Club trip planner to set my routes, bearing in mind they do not show all the campgrounds available in any chosen area so scan the internet for others.
When I returned home for Christmas from Florida I had no problem locating a storage place for my motorhome,and it was not expensive. I am currently looking for somewhere between Seattle and Vancouver to store my motorhome in July when I go home for a holiday (and meet my visa requirements!), which I am finding more difficult. If it comes to it I can always find a cheap 'no frills' campground and pay their monthly rate. I do not think Walmart would appreciate me 'boon docking' on their car park for that long!
I have required warranty work to be done on my motorhome on a couple of occasions. My manufacturer have an excellent Customer Service and have directed me to good local workshops and dealt direct with payment. The only real problem I have met is that workshops are usually very busy and booked up sometimes weeks ahead, so you need to be flexible in planning your journey. I am currently at a campground close to Yosemite N P with a broken windscreen, which has meant an additional weeks stay to arrange a replacement to be shipped and fitted. Insurance cover is something to consider very carefully; my windscreen is covered in my policy, but many are not so ensure you have it. It is not cheap to replace a motorhome windscreen, mine will cost the best part of $2000 to replace, of which I pay the 1st $1,000! Luckily I set a few thousand dollars aside of contingency!
The American RV community are a great bunch of people. Put your home National flag stickers on your motorhome along with a 'State Stickers' map and you will be chatting with your fellow campers before you even set up camp!! I have made many new friends and learned of so many places to visit I had not heard of or considered before. I also put a pretty good schmore together now!