If I am understanding you correctly, I see two issues.
You don’t need (or want) the brackets  or the Open / or Close/ operators - they are inferred in Bubble.
You are trying to use extract with regex to get yourself a list of character groups that AREN’T a group of repeating spaces and then put them back together. The easier solution is to use value:find & replace and check the ‘Use a regex pattern’ checkbox. In the regex pattern input just put \s+ . In the Replace With input just type a space. This just returns your original value with all instances of ANY number of spaces with a single space.
However that was just an experimental trial and I think I have found a bug.
If you apply find and replace to text from an input field the Regex works on display of the data in a text field that works.
If you apply find and replace to a text field resulting from an API query and don’t use regex the transformation works perfectly.
BUT if you apply find and replace to a text field resulting from an API query but do select USE regex pattern (as above) it returns an empty field. In fact no find and replace with any Regex pattern seems to work.