Even Americans who do not know what a FICO score is, care about their credit rating. Every time they want to make a major purchase, or apply for credit of any sort, their credit scores are run. One of the most popular of those scores is the FICO score which, while used primarily in the housing industry, is still an accurate reflection of the overall credit worthiness of a person. Given that anybody applying for credit is hoping to be approved, the desire for a high and/or acceptable score exists, regardless of whether the person knows what that score is called.
They may not care about it all the time, but I guarantee when they go to buy a house or a car they will car greatly what their score is. I think most people are afraid to look or don't know how, or don't know all the factors that effect it.
No, I do not think most Americans care about their FICO scores. Years ago, people were not urged to look at their credit scores. Credit history was a big dark secret that could only be accessed by car dealers and the like. It has only been in recent years that this trend away from "secrecy" has changed. As a result, many Americans are uneducated as to what FICO scores really are.
The poor and marginally poor are fast outnumbering the rest. This is why most citizens do not care what their FICO scores are. Industries have evolved to assist those, who are without acceptable FICO scores, in obtaining what poor FICO scores will not allow. With these benefits, many feel that they can have a reasonably good life despite the constraints of poor FICO scores.