I've already posted on GSS results on science knowledge. But what about the international context? Th working paper Civic Scientific Literacy in Europe and the United States has some interesting data which has international comparisons. Here's an interesting fact regarding "scientific literacy":

This confirmatory factor analysis demonstrates that all 32 of these items reflect a common factor. The uniformly high factor loadings suggest that many of these items are interchangeable and that would be possible to use a subset of these items if one needed a measure of civic scientific literacy and could not collect a set of 32 items.

In short, the data here suggests to me that the stupid within a population are less scientifically literate. That's probably the single factor which explains most of the variation. But note the factor loadings on specific questions:

If you can provide a correct definition for "stem cell" it's highly predictive of scientific literacy. On the other hand, note that the evolution questions have lower factor loadings; I think we're seeing the effect of religious Fundamentalism here. But what about the international context? Here you go....