The USA puts out great free topographic line maps, but I can't find any free (topo line map) resources for the EU with enough detail to model the terrain. While I'd prefer 10m elevation between lines, I'd be happy with up to 100m. Do any such resources exist?
So you are looking for a European wide contour dataset crossing all international borders at a resolution similar to the USA data produced by their mapping agencies? You are not asking for much then...
Do you think the European countries would organise themselves to collaborate on such mapping task? I am happy to be proven wrong!
Your only choices are to acquire each in country contour dataset and splice it into a single seamless data (no easy task but most likely to give you the resolution you are requiring), or use contours created from global datasets (so lower resolution) such as SRTM, a simple search on Google using the search term "contour data europe" threw up Contour lines vector tiles Europe.