That seems an excellent idea, and one that will help people eat more healthily and save money.
How, you ask?
Well, I think if people realize how much of their precious food dollars they are spending on worthless -- even downright harmful -- calories, it will make it easier for them to make adjustments and allocate their money so that they get more nutritional bang for their buck.
But in order for the sugar labeling to be really meaningful for the U.S. consumer, I think they should take it a step further and label the sugar content in teaspoons instead of grams.
Grams are almost completely indecipherable to people in the U.S since we don't use the metric system in this country (I won't go into how ridiculous it is that we don't, but it truly is absurd).
By way of information: 4 grams = approximately 1 teaspoon.