North America
The United States is entirely located in the northwest hemisphere.
No continent can be entirely in opposing hemispheres.
North America and Europe are entirely in the northern hemisphere.
The continent of North America is located entirely in the northern hemisphere and the western hemisphere (or, as we might describe it more succinctly, it is located entirely in the northwestern quadrant).
North America is the continent that is located entirely in the northern hemisphere and western hemisphere.
Canada
No continent can be entirely in two opposing hemispheres. Entirely in Northern: North America and Europe Entirely in Southern: Antarctica and Australia
Antarctica is the continent located entirely in the Southern Hemisphere.
Europe is a continent that is almost entirely in the northern hemisphere, with the exception of a small portion of Turkey that lies in the southern hemisphere.
North America is entirely in the northern and western hemisphere.
Any continent; North America is not correctly considered as a continent.