Final answer:
The European club system and the United States differ in their approach to international politics and organization. The United States' participation in treaties and international organizations is driven by national interests and global influence.
Step-by-step explanation:
The European club system and the United States have special differences primarily in their approach to international politics and organization. The European system is hierarchical, with shared culture and values, while the United States follows its own system. On the other hand, the United States' involvement in treaties and international organizations is determined by several factors, such as national interests, global influence, and diplomatic priorities. This allows the United States to assert its position and exert influence on global affairs. Overall, the special aspect lies in the contrasting approaches and impact of these two systems on the international stage.