J visa holders subject to the two-year rule are not permitted to remain in the United States and apply for an adjustment/change of status to a prohibited nonimmigrant status (for example, from a J visa to an H visa) or to apply for legal permanent resident status (Green Card) without first returning home for two years or obtaining an approved waiver. Whether you are subject to the two-year rule is determined by a number of factors, including your source of funding and your country's "Skills List." It is not determined by the amount of time you spend in the United States.
Citizens of Canada and Mexico may be eligible for NAFTA Professional (TN) Nonimmigrant status if they work in a qualifying profession. TN status is very similar to H-1B status. To be eligible, you must have a higher education degree, or its equivalent, and a job offer from a U.S. employer. However, if you do not have a degree but have acquired similar skills after working for several years in a specialty occupation, you may also be eligible. Learn more about NAFTA work visas.