phranque - 8:37 am on Oct 24, 2012 (gmt 0)

In all these pages the canonical tag points to http://www.example.com/ - english (US) version.

this is an incorrect application of the link rel canonical element.
the content for each language should have its own canonical url.

Having subfolder like http://www.example.com/de will help in verifying the German site and setting its geographic target in GWT to Germany.

having a sudomain will have the advantages mentioned above and also allow the subdomain to be hosted within the targeted geography.
IP location is one of the stronger geolocation signals according to google.