America is one of the countries that grants the most rights to its citizens. This is enshrined in the constitution.
The constitution has always been a thorn in the side of anyone who wants to establish a top-down dictatorship in America.
Imagine a case where such a person or people decide to target certain Americans.
If it is possible to renounce citizenship and the rights it comes with, people might target them with demands that they do so, hence depriving them of their constitutional rights and protections.
The entire bill of rights only applies to U.S. citizens.
For these reasons and to avoid this possibility, in my personal opinion in order to safeguard liberty, it should not be easy, or even possible, to renounce citizenship and the rights it comes with.
If it is possible to renounce constitutional protections, someone could force people to do so.
Hypothetically, imagine if a police officer broke into your home and handcuffed you to a radiator until you were willing to renounce your citizenship.
I personally feel that this is not a scenario that should be possible.
To avoid this scenario, I think that it should not be possible to renounce U.S. citizenship and the rights it comes with.