My two favorite reasons for honoring the U. S. Constitution are: 1) the Founders got some things right and 2) they built a method for improving the document into the document: a method for amending the constitution.
I don't have any interest in honoring the Constitution because the Founders were god-like figures who must not be challenged by lowly people living today. The Founders challenged each other endlessly, setting a good example in doing so.
One definition of an American might be a citizen of an amendable republic.
In a few words, Abraham Lincoln crystalized a further trait of that amendable republic. It is a government of the people, by the people, and for the people. So let's rephrase the previous paragraph:
An American is a citizen of an amendable government of the people, by the people, and for the people.
Lincoln wisely chose to theorize about government in words that can be understood by anyone — such a respectful act on his part. Also hopeful: if we speak to each other in commonly understood words and phrases, we have a chance of holding a productive conversation. Most people like me, professors, no longer bother with writing that way, no longer bother with speaking in public that way either.
Power derives from the people, Lincoln argued: government is, therefore, of the people.
Every politician in the capital of the nation or of a state people believes that they act in the best interests of the people — that they govern for the people. Even if they don't take care to look very closely at the results of their policies and at the needs of the citizenry as a whole.
In a republic, we send off our representatives and don't easily make them stay in touch with our wishes between elections. Some never visit the portions of their districts where the other political party has the most members — many politicians simply write off those folks and their rights to share in governance. Spending time with those people is not productive, a press officer of a member of the Indiana Congressional Delegation said recently. So much for government by the people — when half the country's residents might commonly not be consulted between elections.
Then there's the presidential declarations that have become the common method of governing for Mister Trump. No need to consult the elected members of Congress, just declare a state of emergency and dictate a policy. Surely the more this path is followed, the less a nation has government by the people.
On top of that, the U. S. Constitution has become very difficult to amend.
If an American is a citizen of an amendable government of the people, by the people, and for the people, well, then in current circumstances we can speculate that Americans have lost the most central few traits of their nature, their identity, their civic practice. If so, then we might speculate that Americans as we like to think of them no longer exist.
Because the America from which they drew that identity is gone.