What is America to you? The United States: Are we our borders? Our constitution? To me, we are a nation-state with borders, we are our constitution but perhaps most importantly, we are the Bill of Rights. Without the last one, we are not what I would consider to be "America".
I've always simplified it to the Declaration - "We hold these truths to be self evident; that all men are created equal; that they are endowed by their Creator with certain unalienable rights;..." A bold and noble ideal that I hope we continue to move towards.
We are a nation with defined borders guided by the Constitution.