Complex sentence: A major influence on American writers at this time was Romanticism, which gave rise to New England Transcendentalism, and the publication of Ralph Waldo Emerson's 1836 essay "Nature" is usually considered the watershed moment at which transcendentalism became a major cultural movement.
Split into simpler sentences: A major influence on American writers at this time was Romanticism. The publication of Ralph Waldo Emerson's 1836 essay "Nature" is usually considered the watershed moment at which transcendentalism became a major cultural movement.