How much of "wasabi" is actually wasabi in the United States?

After looking at wasabi's Wikipedia page I was shocked to find out that real wasabi loses the majority of its flavor in 15 minutes if left uncovered and that in the United States "wasabi" is actually horseradish, mustard, starch, and green food coloring.

This made me wonder about much of the wasabi-flavored foods I have had such as wasabi peas, and the ingredients list of Trader Joe's Wasabi Peas confirms that their "wasabi" is nothing more than mustard. However, another brand of wasabi peas simply lists "wasabi" in their ingredients list which makes me wonder if it is legal in the US to label horseradish, mustard, and other things that clearly are not wasabi as wasabi. It also makes me wonder if I have ever had real wasabi in my lifetime living in the United States.

Does anyone have any insight into how much of the wasabi-flavored foods in the United States are authentic and how to know what is the real thing? I am also very interested in knowing more about the regulations that pertain to foods being labelled as "wasabi" when there is no actual wasabi in them.