The overwhelming majority of democratic countries use a parliamentary system that has a separate head of state and head of government. Very few use our idea of combining the two. That would make Canada a model constitution for a country wanting a parliamentary democracy.
Our Constitution has to be interpreted in light of English constitutional and common law as it existed at the Founding. Otherwise, how do you understand the meaning of "due process of law"? But very few countries have a common law system.
We have a federal system that at least theoretically has a federal government with limited powers. Most countries are geographically smaller and want a stronger central government.
It's certainly true that our Constitution was designed for a federalist system of distributed powers between numerous states with their own regionally divergent concerns, not a unitary nation with a single central government where the divisions are ideological, not geographic.
Our American winner-take-all system of districts in an Egyptian context would likely result in virtually no members of the Coptic Christian minority being elected, and in many districts the most radical type of Islamic radicals would get a plurality though not always an absolute majority of the vote.
Proportional representation by political party in a parliamentary system without a strong executive works well in nations where the divisions are ideological or ethnic rather than primarily geographical, and a good case can be made that a parliamentary system of proportional representation has become the majority form of democratic governance in the world because the political fault lines in most nations are no longer based primarily on geography, though geography may be important.
There's also the issue raised by several other Freepers that the founders of the United States had centuries of common law behind them and about a century and a half of self-government as British colonies. A constitution of a nation with little experience in self-rule needs to be far more detailed because nothing can be assumed if it's not in writing.
Quite likely even having things in writing won't help if people aren't deeply committed to the rule of law. Anglo-American jurisprudence had the question of “Lex Rex” — the law is king, not the king is the law — settled by the English Civil War a century before the founding of the United States. That simply is not an unquestioned principle in the Middle East, where strongmen are the norm and laws have only the force the leaders choose to give them.
Let's grant all that. However, what Justice Ginsberg actually said was none of those things, but rather that our Constitution was outdated.
Now maybe she meant something else and was trying to imply things to avoid offending her hosts, but what she said was not good, and quite likely indicates a seriously defective view of the document she's supposed to be using as the basis of her Supreme Court decisions.