What's your Opera?
Tried to find that discussion - but failed. The thing is, you can't change your predefined search engines. People were talking about a possibility to delete the Google one - or like that (like deep tinkering), also they were saying you can add your own ones still...
Did you installed a localised version? I wonder if the international one could still have .com there...
I'm using version 25.0.1614.68 on Windows 7. When I first installed Opera earlier this year I was able to change the search engine to Google.com, but maybe something changed meanwhile. The installer was called "Opera_NL_stable.exe", I'll see if an English installer makes any difference.