The U.S. constitution is anything but a rigid document
Its very brevity makes it accomodating to a variety of historical eras. The secret to its usefulness is that legislators, courts, and the people have to accomodating of change. And they have been, for the most part. Americans start from a naive faith in the sweet nature of progress, and reshape their habits, institutions, and congressional interpretation to make the best out of whereever progress takes them.
There were some rascals in the early and mid 19th century who resisted progress, but we had a transformative little war and fixed them, more or less.