Great example. You’ll just want to change, “in respect of” to “with respect to” if you mean “regarding.” So you can say, “Many Americans had a deep change of heart with respect to the US judicial system due to the outcome of the Casey Anthony trial.”

Great example … just say, “…and many voters have a change of heart when the promises aren’t fulfilled.”

The only change I would recommend is to put “has” in the past – it’s something that happens in an instant, so you’ll almost always want to use it in the past, future, or infinitive: “The government had a change of heart,” or “I predict the government will have a change of heart when food prices start rising” or something like that.