Why does the South American cold desert experience less-severe
cold-weather outbreaks than does the North American cold desert?

Silvers --

Antarctica buffered by a large barrier of water, which has consistent
heating and cooling characteristics.  Indeed, it sets up a consistent
wind flow around the continent, which itself is a buffer.

By contrast, the north polar regions are surrounded by large land
masses which absorb heat readily in the summer months and provide
significant changes in heating.

Best regards,

Omnivorous-GA

Quite right.  The extremes of continental climate experienced in N.
America and Eastern Europe and Siberia do not occur in S. America for
this reason.
The Atacama desert is actually in the temperate zone and hence not
subject to very cold winters.  But being above 3000 meters, of course
it is rather cold.
It is considered the driest place on earth.

Hope this helps, Myoarin

Thank You Omnivorous and Myoarin. Your comments were very helpful. I
appreciate you taking the time to help me.

Silvers,
My pleasure, and thanks for responding.
Myoarin