One thing that is unique to the US implementation is the limitations inherent in the Federal Constitution.
The Federal Government has specific rights that are enumerated in the Constitution, and anything else is literally reserved for the States and the People.
This means that the people will never be subservient to the Federal Government.
Old Blighty doesn't have that feature.
Really, just because they don't exist in the form of a written consitution doesn't mean they don't exist in some form or another in one of the many laws that have been passed throughout the centuries.
If they are not written into the constitution, they can theoretically be changed.
There is no constitutional protection in any other constitution I can think of.
The protections in law, and external to the constitutional framework, are a happy evolution of the democratic process, rather than a feature of the system in place.