According to the device specifications for the Asus Eee Pad Transformer Prime:
Connectivity 802.11 b / g / n, Bluetooth 2.1 + EDR
By a scan performed using inSSIDer 2.1
I'm from Portugal - Coimbra, and my 802.11 b/g/n is set to channel 6 to 10.
Other networks around my location are spread from 1 to 14.
According to the 802.11 b/g/n specifications, channels go from 1 to 14. Portugal has them all.
See this Wikipedia - List of WLAN channels (scroll a bit down to see the comparison table).
All flags are green to use that device in Portugal.
As you've mentioned at the comments, US uses 110V, Europe uses 220V.
This is easily overcome by the usage of a transformer:
Amazom :: Goldsource® STU-100 Step Up/Down Voltage Transformer Converter - AC 110/220 V - 100 Watt
The wall plug can be used in the US or Europe.
The output is either 110v or 220v, depending of what you need.