Our research has found that to work legally in the USA, a Canadian Citizen must have a work visa in most instances

Types of Work Visas are explained here:
http://www.canadausvisas.com/usa-immigration/usa-work-visa-permits

More on the H-1B Visa:
http://www.canadiansinusa.com/Working-in-the-US/h-1b-visa.html

Step-by-step process:
http://www.wikihow.com/Work-in-the-Usa-As-a-Canadian-Citizen

The U.S. National Park Service accepts non-resident volunteer applicants and often has RV sites:
http://www.nps.gov/oia/topics/ivip/ivip.htm

The U.S. Army Corps of Engineers offers exceptional camping opportunities and accepts non-resident Workamping volunteers:
http://corpslakes.usace.army.mil/employees/faqs.cfm?Id=volunteer

Filing IRS Form 8840 with the U.S. Government

If you are an alien individual and you meet the closer connection exception to the substantial presence test, you must file Form 8840 with the IRS to establish your claim that you are a nonresident of

the United States by reason of that exception. Form & instructions.

We recommend that you first contact any campground or organization you are interested in working or volunteering with and discuss your experience and their requirements.