Question
I run an international shipping website, so my audience range is very wide since I can target users from all different countries.
However, would I have greater "website growth" if I target 1 country at a time using "highly-targeted landing pages / ads" for users in that country to optimize my conversions as much as I can and then move on to other countries afterwards doing the same thing?
Answer
A more niche site almost always converts better than a broad site.
A targeted site allows you to use specific language and terminology that will resonate with your audience. Trying to be all things to all people dilutes your message and ultimately cost you a considerable number of conversions.