National Treasure/National Treasure: Book of Secrets (2004/2007 film) = Finished

The National Treasure movies are a strange anomaly. Produced three years apart from each other, they are perhaps the most cohesive sequels of all time--there's a time skip, but they feel like they were made within days of each other instead of, well...years.

Both feature sympathetic-yet-ruthless antagonists.
Both feature Nicolas Cage acting alternately normal, and Very Much Not.
Both feature high-tech leaps of logic, energetic and characterful heisting, and feisty dialogue that is generally delightful.

All of that said, the movies themselves don't rise above the sum of their parts. The mysteries at their core, and the resolutions of those mysteries, are simply okay. This baffled me, especially when I tried comparing it to its nearest predecessor--Indiana Jones.
They're both globetrotting adventure movies about the importance of historical artifacts, so why does National Treasure feel like it's missing something?
It was a question that took me a while to figure out, but I think I've found the answer.

National Treasure tries to invest a young nation with historical weight that it simply doesn't carry, using tales that primarily affect that nation.

The Holy Grail from Indiana Jones and The Last Crusade? It's a legend that goes back almost a thousand years, crosses political and cultural boundaries across the Western world, and forms the essential myth of at least one country. The Ark of the Covenant is an artifact that goes even further in terms of its age, multi-cultural reach, and inherent meaning. The locations that Indiana and his quirky crews go to have long memories--textures that the audience can feel even as Indy skips across their surfaces in his own journeys.

As of this writing,  the United States is about 243 years old.
On a global scale, we are babies.

You can invoke the Founding Fathers, Freemasons, the Knights Templar, or even a lost Native American city of gold, as much as you want. While unfortunate (especially in the case of the Native Americans), the perception of these parties is quite modern. Their names and mysteries have some significance elsewhere, as seen when the second movie took us to France and England--but the priority is first and foremost placed in our culture. This perceived youth isn't helped when the movies pull in modern conspiracy theories to recontextualize their subjects, either.

I believe this lack of historical weight is part of why the movies increasingly tie their mysteries to the main characters themselves. In the absence of the perceived, inherent value of the past, we can at least have an investment in a mystery's personal connection and impact on our heroes.

So, yeah.
In National Treasure, we aren't solving ancient puzzles, but new ones.

It doesn't just feel less groundbreaking--it feels less important.