Having Sharia Law mixed into the fabric of the laws of any nation would make for bad government. Being influenced by the false teachings of Islam can’t lead to a good place.
Having people in a government who are surrendered to Yahweh can cause even a generally corrupt government with bad laws to become good government. The opposite is not as likely to be true though: having the best laws, but having immoral and unbelieving people ruling in it would still be bad government.
Daniel, David, Mordecai, Esther, Hananiah, Mishael, and Azariah (three friends of Daniel who were given the demon glorifying names Shadrach, Meshach, and Abed-Nego) were all government officials who influenced the nations in which they served. As we pray for believers whom Yahweh has called to bring His presence and rule into the governments of our cities and nation to hear and to accept their callings, we will see His Kingdom influence our cities and nations in ways we have not yet.