What associations do surnames with “de,” “du,” and “le” have in the US?

I was reading The Scarlet Pimpernel and came across surnames such as de Tournay and de St. Cyr, which got me wondering about surnames with prefixes like "de," "du," and "le."

In the US, what kind of first impression, if any, do these surname prefixes give you? Do they suggest a particular country, region, social class, or historical period? Would you find it unusual if someone with no apparent European background had one of these surnames?