When using a foreign address on a card... as long as you have american dollars in the account, the zip code is 00001. Did it last night for my phone bill. Most sites wont take 00000 as a valid zip so I tried adding the 1 and it worked.
When providing services internationally, two kinds of taxes are relevant:
sales taxes or VAT
These are completely independent.
There is a US–German tax treaty. When providing independent professional services, the location where you perform your service or have your establishment is relevant, but the location of the ...