In Britain, where I live, there isn't a distinction between constitutional law and ordinary statute law. Any law can repeal or amend any other law, and all laws follow the same procedure to be passed.
The only exception is that a law to extend the term of the House of Commons can be completely defeated in the House of Lords, rather than merely being delayed one year, as any other law could be.
Note that a law abolishing the House of Lords could be passed after the one-year delay.
Different countries put different things into their constitutions, and have different degrees of entrenchment of their constitutions. What commonalities can we draw between these? What constitutional provisions are very unusual to include? What provisions are very unusual to omit?