Why did the poet Ralph Waldo Emerson call the first bullet fired in Lexington "the shot heard round the world"?

It started a revolution that brought a new nation to the world scene- the United States of America

The sound from gunfire was so loud it could be heard for hundreds of miles.

Immediately after the battle of Lexington several superpower countries such as
Spain and France came to fight alongside the colonists.

Emerson wanted to make a point that this war consisted of gunfire instead of
other fighting techniques.