Final answer:
Barack Obama expresses the concept of America as a nation built on solid ideals and principles, despite its challenges and shortcomings.
Step-by-step explanation:
Throughout the text, Barack Obama expresses the concept of America as a country built on solid ideals and principles, despite its challenges and shortcomings. He emphasizes the importance of coming together as a nation and working towards a better future, beyond racial and partisan divides. Obama's speeches and campaigns aimed to inspire and motivate Americans to believe in the potential of their country, while acknowledging the need for progress and change.