Final answer:
Meetings between prime ministers and US presidents address significant bilateral and global issues, shape foreign policy, and often symbolize important historical shifts in international relations.
Step-by-step explanation:
The meeting between the prime minister and the US president is usually called to address significant bilateral and global issues that impact the two nations involved. For instance, when former US President Barack Obama and Canadian Prime Minister Harper met, they announced a shared vision for perimeter security and economic competitiveness between Canada and the United States. Throughout history, from the Atlantic Charter discussions between Churchill and Roosevelt which defined post-WWII goals, to the more recent presidential summits like the Malta Summit symbolizing the end of the Cold War, and Obama's engagements with foreign leaders, such meetings have been pivotal in shaping foreign policy and international relations.