P.S. I would think the Alexa - Honeywell 'Skill' is in the US version as well.
http://yourhome.honeywell.com/amazon-echo
P.P.S. I noticed you can change the Language now between English (UK), English (US) and German in the Settings | Language option of the Alexa App...
Perhaps this the 'Skill' and the voice are all you really wanted?
From what I read this is not the same as changing the devices registered Locale. Changing the local had to be done 'manually', at least for the moment.
Of course that could change, due to data protection and other legal framework influences. 'Caveat emptor' though....