Ideally, shouldn't the United States have a unicameral, purely representative government?

The notion that states should not exercise their sovereignty is a dangerous one. If you don't agree with the laws in your city, you move to another one. If you don't agree with the laws of your county, you move to another one. etc. etc. If we "merge" everything into one nation, where can one go to be free? We are heading toward a world order at a record pace lately, and we could very well be the last generation to enjoy what little freedom we have left.