Are you wanting to buy foreign *currency* or foreign *companies* (stocks)?
Buying foreign currency is... not, I mean, in the case of your home currency being the Euro which is one of the most widely used ones, just not worth it. I've never seen anything recommending holding bonds in a country that you do not live in, for developed nations (Greece? Sure, but that's about it).
If you want stock, just buy a Euro-denominated US index fund. Try vanguard; they have funds in many currencies.