How did the panama canal exemplify american technological prowess?
how have politics and technology made the twentieth century the "kiling century "?

For the answer to the question above, No one else could build that canal. The Americans are the only one who can build them. they also invented Panama so that we could the necessary territory.

The forging of large, powerful nations into "power-blocs" vying with each other for control, coupled with the emergence of extremely lethal weapons of war (machine guns, bombs, aircraft and nuclear weapons)