Using country codes for languages may confusing. I expect that US visitors should be served the UK pages and that people from Austria and part of Switzerland are targeted by the German translations. That may not be obvious for first time users and they may leave your site because they might think you are not targeting their country.
I personally prefer a third method page.lang.html, because this naming convention is compatible with the automatic browser language negotiation in the Apache webserver which takes place when a browser connects to the webserver.
In practice if people go to www.example.com/page then the server automatically serves www.example.com/page.en.html to visitors with English as preferred setting in the browser, www.example.com/page.de.html for German language visitors etc. The only drawback of this naming convention is that you need to be careful to get all the different language versions properly indexed in the search engines.