100 degrees west will put you somewhere in the American continent. You can't go 100 degrees south, as 90 degrees will put you at the south pole !
North America
60 N 100 W is Nueltin Lake, Canada.So the continent is North America.
South America
South Dakota
The South Pacific Ocean.
90 degrees south latitude is the precise location of the South Pole. The South Pole is in Antarctica, a continent of quite some size. It contains no oceans. The South Atlantic runs from the Equator to about 77 degrees south and from 20 degrees east to 65 degrees west
That point is in Nicaragua, about 100 miles northeast of Managua, in Central America. This area is part of the North American continent.
44 N 100 W is south Dakota and a point west of the Missouri River
Mexico City
That point is about 0.9 mile south of US-212 in Gettysburg, South Dakota.
40 S 100 W is in the South Pacific Ocean, far off the coast of Chile, South America.
45 N 70 W is Central Somerset Township, in the state of Maine, USA.