Chemically, in an acidic and water environment like a can of soda, sucrose will quickly break down to the simple sugars in which HFCS has less glucose. So unless you're getting cans only a day or two from the factory, they're pretty much the same sugar-wise assuming the same mg/L (which they might be different, I don't know!).

What are the labels? Are the total sugar content that different? (EDIT: Rereading, only 2.5% off...by volume or DV%?) Because if they're the same, the European coke would have a smidge more free glucose than an HFCS-55 would have by definition.