Based on what I've read from Amar, he's far more concerned with the text than most who have a progressive or "living constitution" view of our Supreme Law. He's not afraid to say the text doesn't support a given court decision or interpretation of a clause.

I don't think he's wrong. I don't quite agree with him, but he's not wrong, imo, that the sovereign (we, the people) can alter the meaning of the text or grant new powers to Congress through long, popular acceptance of that power. Social Security and Medicare are the main examples. For nearly a century, We, the People have refused to rescind those powers Congress declared for themselves. We've had ample opportunity, and we've not done it. It's not a simple thing to determine when this has happened, or to say X number of years means something is now constitutional. But there comes a point when one becomes as ridiculous as Don Quixote without his dignity to keep tilting at something that enjoys immense popularity.

There are less controversial (imo, anyway) ways in which the unwritten constitution impacts the meaning of the text. At the dawn of the Republic, those who constituted "the people" were a much smaller subset of the Republic's population than we recognize today. The meaning of "people" in the text has changed as our understanding and recognition of who "the people" are has changed. Some of that change was represented in amendments, but no amendment expressly establishes the meaning of "the people."

“Nobody has a legitimate reason to fear a faithful interpretation of the Constitution, and nobody has any legitimate reason to fear effective and complete protection of civil rights." - Alan Gura