You should be able to use mod rewrite to solve this by adding lines to your .htaccess file, allowing anything on your country domains 'www.myEnglishDomain.eu/{wildcard}' to be rewritten to the country path '/en/{wildcard}'.
First you must make sure that the bindings for each domain are pointing to this website.
Then add the following lines to your .htaccess file:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^www.myEnglishDomain.eu$[NC]
RewriteRule ^(.*)$ /en/$1 [L]
RewriteCond %{HTTP_HOST} ^www.myGermanDomain.de$ [NC]
RewriteRule ^(.*)$ /de/$1 [L]
If you need the domain within the browser to update to myDutchDomain.nl, then doing the following instead:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^www.myEnglishDomain.eu$ [NC]
RewriteRule ^(.*)$ http://www.myDutchDomain.nl/en/$1 [R=301,L]
RewriteCond %{HTTP_HOST} ^www.myGermanDomain.de$ [NC]
RewriteRule ^(.*)$ http://www.myDutchDomain.nl/de/$1 [R=301,L]
For further help, here is a mod rewrite cheat sheet: http://www.cheatography.com/davechild/cheat-sheets/mod-rewrite/
Disclaimer: I have not been able to test the above rules, please let me know if this contains syntax or other errors so to maintain an accurate reference for other people.
