Not if we speak with nuance. Ancient civilizations were often linked by trade routes too. Western Civilization dominates the world, and other civilizations and uncivilized regions have Westernized to varying degrees, but in places important cultural differences remain. There are still fundamentally non-Western aspects to the Islamic world, China, and much of Africa and other Third World regions.
But the scientific society responsible for modern transportation and communication is Western and broadly encompasses the earth, so in some narrow senses it makes sense to speak of humanity as currently having one civilization.