What is the best strategy for making a group of wordpress sites to target multi-countries
I would recommend one of the Multilingual plugins for this (I use Polylang most of the times) if the content is the same for all languages and you need just translation.
But if you are thinking of having different websites targeting different markets I would use WordPress Multisite to build a network of websites.
It can be a network of subdomains for each language/country (en.site.com, es.site.com, de.site.com) or Top Level Domains (site.us, site.de, site.es etc).
Check out my talk about using WordPress Multisite for these types of cases https://sabrinazeidan.com/wordcamp-london-2018/ (Starting 20:41 in this video)
