Well, I can't give you step-by-step guidance, but you would need the following:
1. Static IP address (or dynamic DNS) for your home laptop - just to know where to reconnect in case you have problems
2. OpenVPN installed on your laptop/proxy. This should get you started: http://openvpn.net/index.php/open-source/documentation/howto.html
3. recliq's (or was it RMerlin's?) openvpn.app.bin (it's in the repository if you are running 0.5)
By the way, with the openvpn app bin I think you can connect the other way around too - meaning - leave the wdtv at home (always on) and take your laptop and connect to the wdtv. The wdtv would only work as a network proxy.
Use the howto to learn how to configure a VPN tunnel between your wdtv and your server. You should be able to inject a default gateway through the VPN tunnel, and then all your traffic would go through the proxy and appear as local in the US. It will take some trial and error, so you'd better test it a bit before leaving.
Please note that even if you get it to work at home, you might have issues with your internet provider abroad - depending on the connection type, they might filter IPSEC and your tunnel will not connect (I've seen this on free wifi connections, or when the provider really wanted its subscribers to buy VPN tunnel service instead of building it themselves)