In cooking terms, corn syrup in this country is very often referred to as glucose. But it is not pure glucose; it also contains a fair bit of another, more complex, sugar, dextrin. Also, in that corn is largely an American crop, corn syrup has not been widely available in Europe. So your European cookbooks are really calling for pure glucose, which has probably been processed from grapes or honey.

Pure liquid glucose is available in supermarkets in Europe, but is harder to find in the US. So now that you've learned all that you need to, either track down some glucose, or use light corn syrup in your baking and frosting projects. After all, who's going to notice a little extra dextrin?