BasicGreatGuy
Aut libertas aut mors
Is the US still locked into an 18th Century mindset because of a written constitution?
Only if you're what's commonly referred to as a strict constructionist. Others who look to a four corners interpretation of the document and/or incorporate precedent into their decisions create the flexibility to keep the Constitution from stagnation. The tricky part is the balance between adherence and flexibility. But I digress.
What keeps the Constitution from being "stagnant" as it were, is the ability to amend said document via Article V.