Because of what America is and what America has done, a firmer courage, a higher hope, inspires the heart of all humanity (1.7).

How awesome is the U.S.? Not only did we have to help settle Europe's bloody conflict, we then provided humanitarian aid to help rebuild the ruins. The motif of humanity, and how it should be embodied in American values, runs throughout Coolidge's speech. He gets a huge amount of traction from the U.S.'s role in ending World War I and financially helping Europe recover.

After all the death and destruction that the former powerhouses of the world just inflicted on millions of people, the U.S. was the country that had tried to avoid war, and when that was impossible, helped to pick up the pieces. And we wouldn't stop there:

We have not failed, nor shall we fail to respond, whenever necessary to mitigate human suffering and assist in the rehabilitation of distressed nations (10.4).

We are the poster child for the human race.

There could be a number of reasons why Coolidge would emphasize the humanity of American citizens and the nation overall. He could be trying to push against the tide of modernization that was brought on by the war and industrialization. There were a lot of folks who thought America's morals were decaying as a result. Plus there was all sorts of new (non-human) machinery, like cars and mechanized manufacturing, so an emphasis on the human side of things would be appealing.

Or maybe Coolidge knew that plenty of Americans resented their European counterparts because of the war they dragged us into. He's reminding us that even though we're an ocean apart and don't want anything to do with them politically, Europeans are people, too, so we have to acknowledge our shared humanity.