It is probably not the best advice to block slow countries or regions with the goal of improving your Google search rankings. Yes, Google has a page experience algorithm that is mostly made up of speed factors from its core web vitals. But it is such a light weight factor, the benefits you'd see from blocking those users would not outweigh the negatives you see from blocking those users.
This is a question that has come up numerous times before and the answer has always been, do not block these users from slower internet regions.
John Mueller of Google addressed the question again, this time on Reddit giving another reason not to block these users. He said "if a country is skewing your overall CWV results, that means you're getting significant traffic from that country, so if you were to block that country, you'd lose significant traffic. Do you want significantly less traffic?" That is an excellent point.
Okay, so many you don't want those users - that is a different topic. But to block them because it slows down your core web vitals makes no sense. Google said "as we have said before, while this update is designed to highlight pages that offer great user experiences, page experience remains one of many factors our systems take into account. Given this, sites generally should not expect drastic changes. In addition, because we’re doing this as a gradual rollout, we will be able to monitor for any unexpected or unintended issues." It is not a big enough factor or set of factors to block whole regions of users.
Then, John outlines in some serious detail, how to see which regions of users are slowing down your core web vitals metrics. Google added these regional breakdowns in 2018 by the way. He said on Reddit "If you want to roughly see what metrics users in different countries are seeing, depending on how many data points your site has, you can *roughly* compare that with Crux country-level data using Bigquery. You'd still need to use whatever user-analytics you have to determine which countries, and how much traffic from those countries would be at play though (so you might see here it's slow in Indonesia, but not whether it affects a lot of users). Doing this in BigQuery is pretty cool (imo, but I'm just happy that I figured it out), and a limited number of requests/month are free."
He then gets pretty technical into how this is done in the post, so check it out.
But again, should you block countries or whole regions because those regions have slow internet speeds. The answer is almost always no.
Forum discussion at Reddit.
