I have a plan that I unfortunately can't implement due to a lack of networking knowledge.

I use Windows 7 and have an AVM router (FRITZ!Box Fon WLAN 7170 - quite popular here in Europe) with several devices connected to it:

Computer (LAN)
Notebook (WLAN)
Xbox 360 (WLAN)

Without changing the connection type I would occassionally like to assign an IP from the USA to some of the devices (preferably being able to switch it on and off) via one of the paid VPN providers.

Is it in any way possible to do this like I am imagining it? I wouldn't mind buying additional hardware.