Tremors of your network
cause kings to disappear.
Your open mouth in anger
makes nations bow in fear.
Your bombs can change the seasons,
obliterate the spring.
What more do you long for?
Why are you suffering?
You control the human lives
Many countries have the technology to attack others with bombs, but the U.S. military is the most advanced (and perhaps the most active) in the world. Angelou here is referring to nuclear weapons, most notably  the fatal U.S. bombings of Hiroshima and Nagasaki, Japan, in 1945  during World War II. 

These Yet to be United States