Final answer:
Mark Johnson's goal to unite the world through song faces challenges such as language barriers, lack of funding, and resistance from governments.
Step-by-step explanation:
Mark Johnson's goal to unite the world through song faces several challenges. One of the biggest challenges is language barriers as different countries have different languages, making it difficult to communicate and collaborate effectively. Another major challenge is lack of funding as organizing a global music initiative requires financial resources for travel, production, and promotion. Additionally, resistance from governments might pose a challenge as some countries may be unwilling to support or participate in Johnson's initiative for various reasons.