Hi Nuno,
You can not change the domain of the radio from American to ETSI, however on the client card you can enable the World mode feature
http://www.cisco.com/univercd/cc/td/doc/product/wireless/airo_350/350cards/windows/incfg/win_ch6.htm#xtocid3
Selecting this check box enables the client adapter to adopt the maximum transmit power level and the frequency range of the access point to which it is associated, provided the access point is also configured for world mode. This parameter is available only in infrastructure mode and is designed for users who travel between countries and want their client adapters to associate to access points in different regulatory domains.
Default: Deselected
Note This parameter is available only for 2.4-GHz client adapters.
Note When World Mode is enabled, the client adapter is limited to the maximum transmit power level allowed by the country of operation's regulatory agency.