No.
Alaska is the largest mainland state in the United States by land area.
The Australian Outback is probably the largest part of Australia.
Canada is the largest country in North America. Mainland China is in Asia and Mexico is in South America.
Siberia
Not only the largest be the only volcano to erupt in the U.S. mainland in the past 50 years was Mount St. Helens.
Crete
The largest land region of New York would be the mainland.
guyand
The mainland but if you wanted other islands I'm sorry
Crete is the largest Greek Island at 8,336 km².
Mainland (sometimes known as Pomona) is the biggest of the Orkney Islands.