I've long thought that every amendment and major law needs an expiration date upon which time the current legislative body is forced to vote to uphold it or let it expire.

We shouldn't have these because we have sanctified them, we should have them because we still believe in them. If we don't believe in them anymore, they need to go.

13th amendment

Usually "country's values" are something the state or the population publicly (claim to) hold. Another perspective is what others view as their values.

It's not a clear cut thing at all. Americans often use terms like "freedom, liberty, democracy", stuff like that so I'm thinking from their pov those are their values.

Money.

Money is the only truly American value, everything else can be discussed about depending on how much money is involved.

You have a lot of catching up to do in school. The declaration and constitution heavily pull for Locke’s Treatises of Government and even older texts. It is not necessarily speaking to a god. In fact Locke brings up Spinoza in making this point. It is moreso that we exist in a universe that functions with certain parameters that are the baseline for our current situation. It’s very generalized. Basically, Locke’s philosophy, which was inherited by the framers of the declaration/ constitution/BoR was that civil society only exists as an agreement among people in order to better their quality of life. If it does not live up to these expectations, people can abandon government and go back to less civil times. Government helps prevent the breakdown of discourse with war being the ultimate opposite of civil society. Basically, the government exists by the people and for the people. The Declaration of Independence is an important founding document in US history for many different reasons, but one of them that is of importance is that is marks the foundation for a unified set of values that would be further codified in the follow-up documents. It was made very clear to all present that when the Constitution was drafted, it would have fast-follow amendments and then continue to in order to reflect the basic foundational values as society and technology progressed over time. This flexibility was intentionally added. The founding documents don’t speak much about the financial system. That came later.

Jefferson was an athiest too, and he wrote that text.

The Declaration of Independence is a statement of values, a list of the ways the Crown had violated those values, and a list of the ways they felt were proper to address those violations, up to and including armed revolt.

The Constitution was an attempt to make a goverment based on those values. It was and is flawed, and should be changed to better reflect those values. That's why "What about the 3/5 Compromise?" isn't a gotcha. It's wrong, everyone knows it's wrong, schoolchildren are taught it's wrong by the government itself.

I think they come from the European Humanism and Enlightenment, they are not American specific. Equality in rights and opportunities, social liberalism, economical liberalism, religious/origin tolerance, rationality, democracy.

There's some overlap between the two.

I think what makes something some country's values is either the government publicly adopting or enough of the population doing so. That doesn't mean anyone is actually living up to those values. Might not even be trying.

And then there's the question, their values from whose perspective? Americans might say thing X is their value but outsiders might look at them and conclude their value is Y. So there's no one set of coherent values that hold true from all perspectives.