Would some Americans be happier if Christianity and "Christian Law" was imposed on all her citizens?

I'm a Christian, and I wouldn't. If you want to get someone to do something, you use reason, incentives, etc. But you don't use force or threat of force. It's just unacceptable. At any rate, I highly doubt such a system would even work. There is no way you can force someone to believe someone beyond physically tampering with their mind, which is dangerous and does not represent true belief. The mind is a personal area and what a person thinks is something the government cannot and does not have a right to know.