Benjamin Franklin said: "Our Constitution was made only for a moral and religious people. It is wholly inadequate to the government of any other."
In other words, something noble like the Constitution only works for decent human beings who have a conscience.
It does not and cannot work for evil, psychopathic criminals who have absolutely no conscience, because they will utterly ignore it and do whatever they want.
The United State Consitution, much like the Ten Commandments, is simply a set of guidelines for decent people who want a better life. There's nothing inherently in it to force anyone to behave, so the psychopaths don't.
It's up to the rest of us to deal with them.
You're also failing to take into account the history of Liberia. It's not necessarily the culture there it's more along the lines of the fact that the freed slaves who colonized Liberia essentially enslaved the local population and created probably one of the most brutal apartheid systems in human history. Liberia is a shithole today because the system they created was completely unsustainable. A two-tiered society where one class of people has their own set of laws that they follow where they can also do whatever they fucking want to the second class and the second class has no actual way to seek redress against their grievances is doomed to collapse. A perfect example of this is Sparta with the helots. That's basically what the people who founded Liberia were trying to do. It's not going to work. Either everyone gets a spot at the table or the table is eventually going to get flipped over and no one gets to eat.