Route::pattern('param', '[a-zA-Z0-9_-]+');

$euDomains = ['domaina.eu', 'domainb.eu', 'domainc.eu'];
$usDomains = ['domaina.com', 'domainb.com', 'domainc.com'];

foreach ($euDomains as $domain) {
   Route::domain($domain)->group(function () {
       Route::get('/somepage/{param}', 'HomeController@somePage');
   });
}

foreach ($usDomains as $domain) {
    Route::domain($domain)->group(function () {
       Route::get('/somepage/{param}', 'HomeController@somePage');
    });
}

Does this help you?