Complex sentence: With the founding of the Green Party of the United States, the party established a national political presence becoming the primary national Green organization in the U.S. eclipsing the earlier Greens/Green Party USA which emphasized non-electoral movement building.
Split into simpler sentences: With the founding of the Green Party of the United States, the party established a national political presence. GPUS became the primary national Green organization in the U.S., eclipsing the earlier Greens/Green Party USA, which emphasized non-electoral movement building.