*** For United States Only ***
In General, Web Assist seems not to realize that the world not only consists of American customs and American Language. Have you ever seen British zip codes / phone numbers? French? German? Polish? Russian?
As a European you have to consider multilingual issues. So, this extension should be more flexible in adjusting to these issues.
This really has less to do with WebAssist and more to do with Adobe. Unfortunately, Adobe's spry validation has two choices for things like phone numbers - and they are US/Canada or you can choose "Custom Pattern."
I am not sure if Adobe sells a product in Deutschland, do they change the two options... maybe a German user can inform everyone on this.
But, I do know if you want to make it easier to do validation on international numbers, it is not that hard... all you have to do in your CSS Form Builder is edit the validation (which changes the spry) and select "Custom Pattern" from the selection item inside the Form Builder... then once your form is generated, select the blue spry tab that holds the validation for your field and then simply put in your pattern for validation.
With the WebAssist server validation, just double click the server validations in the server behaviors window and then check the validation for the phone number, for example, and make sure it is checked to allow international numbers.