Atlas by Kay Ryan

Extreme exertion
isolates a person
from help,
discovered Atlas.
Once a certain
shoulder-to-burden
ratio collapses,
there is so little
others can do:
they can't
lend a hand
with Brazil
and not stand
on Peru.

Analysis 

The first stanza centers around the use of an allusion to greek mythology. Atlas bears the world on his shoulders. He is the titan who supports the heavens. 

This "extreme exertion" is so monumental, that others can't help when the "shoulder-to-burden ratio" is overcome. Once the system of aid collapses, people "can't lend a hand".  By specifically mentioning Brazil and Peru in the second stanza, it can be assumed that Ryan is talking about foreign aid and how it is often a failure because we only step in after the "ratio collapses". 

The message is clear, to avoid isolation and a collapse of what a country can support, people must intervene before it is too late to help, before we have to stand on Peru to help Brazil.