Hey. You can create new searches for searching Google in English and the English Wikipedia, and set custom keywords to use them.
Go to the search engine settings (opera://settings/searchEngines)
Create a search that points to the location https://en.wikipedia.org/wiki/Special:Search?search=%s with a custom keyword (e.g. "wk") and title
It's a bit trickier to use Google.com as someone in the US would see it, because Google is forcing local results mixed in with English-language results even when you force it to stay in the Google.com domain. You can try it to see what I'm talking about by creating a search that points to the location: https://www.google.com/search?hl=en&q=%s&gws_rd=cr
A workaround is to use a parameter to filter out domains from your country. For example, if you are in France, you can use this: https://www.google.com/search?hl=en&q=%s+-site:fr&gws_rd=cr