If the whole world were merged into a single country, there would certainly be numerous obstacles and challenges to overcome. Here are some potential obstacles that could arise:

1. Governance and Politics: Merging the entire world into a single country would require establishing a unified system of governance that represents and accommodates the diverse interests, cultures, and values of different regions and populations. This would involve addressing issues of governance structure, decision-making processes, and political representation.

2. Legal Systems: Harmonizing legal systems across different countries would be a complex task. Legal frameworks, laws, and regulations would need to be reconciled and integrated, taking into account variations in legal traditions, cultural norms, and social practices.

3. Economic Disparities: The world consists of countries with varying levels of economic development, income inequality, and resource distribution. Merging these economies into a single country would require addressing significant economic disparities, ensuring fair distribution of resources, and managing the transition from different economic systems.

4. Cultural and Social Integration: The merging of diverse cultures, languages, and social norms would present challenges in terms of fostering social cohesion, promoting inclusive identities, and respecting cultural diversity. Efforts would need to be made to bridge cultural gaps, promote understanding, and address potential conflicts.

5. Infrastructure and Services: Integrating global infrastructures, such as transportation networks, communication systems, and public services, would require significant investment and planning. Ensuring adequate infrastructure and services for all regions and populations would be a complex logistical challenge.

6. Security and Defense: Merging the world into a single country would require addressing security concerns and establishing a unified defense system. Cooperation and coordination would be necessary to ensure the safety and protection of all regions within the new country.

7. International Relations: The merging of the world into a single country would have profound implications for the existing system of international relations, including diplomatic relations, trade agreements, and global governance structures. Realigning these relationships and establishing new frameworks would be a complex process.

8. Identity and Nationalism: Merging the world into a single country would raise questions of identity and nationalism. People may have attachments to their existing countries and may resist the loss of their national identities. Balancing global unity with the preservation of cultural and national identities would be a significant challenge.

It's important to recognize that merging the world into a single country is a hypothetical scenario with numerous complexities and uncertainties. The obstacles mentioned here are just a few examples, and the actual challenges would depend on a wide range of factors and circumstances.