Context:
We're currently working with an industrial equipment company, that has its catalog on a prestashop installation. This company heavily relies in SEO and organic traffic to generate its leads.
A concern has been raised because every morning they receive dozens or hundreds of requested from interested customers in Russia, China, Saudi Arabia etc. but they only sell inside the United States.
We explored the option to block all traffic aside from USA, and it worked perfectly, but we got terrified when we started receiving emails from google, stating that they crawling spider could not access our site, which in part lowered our indexed pages, which was a disaster.
For some reason we thought that google crawled from within the US, but apparently they crawl from everywhere.
For this reason, we decided to lift the firewall and allow traffic from everywhere until we can be sure we're doing it in a correct way.
There is even some json feeds, directly from google, which they apparently give you an updated list of all their ips so you can whitelist them. Maybe we'll explore that route in the near future.
See google json ips below:
https://developers.google.com/static/search/apis/ipranges/googlebot.json
For en easy guide on how you can block traffic, you can check below.