Looking at the WJP Rule of Law Index linked above, it's considering factors like constraints on government powers, absence of corruption, and fundamental rights

Looking at the WJP Rule of Law Index linked above, it's considering factors like constraints on government powers, absence of corruption, and fundamental rights. As someone involved in law in the US, the US is really good at these types of things. People, including Americans who have lived here their entire lives, are consistently amazed when they learn the power of the court and how functional it all has managed to be.