I would suggest GNU **`grep`** approach:
Sample `input.txt`:
User\ Name My\ Password
first\ field second\ field
* * *
Cut the 2nd field from _2-columned_ file:
grep -Po '[^\\]\x20\K.*' input.txt
The output:
My\ Password
second\ field
* * *
Or the same with **`sed`** :
sed 's/.*[^\\]\x20\(.*\)/\1/' input.txt
**\----------**
The crucial regex pattern part is `[^\\]\x20` that matches a space `\x20`(space hex code) if it's preceded by any char except escaping backslash `[^\\]`