Direct speech:
M: What kind of traffic from your advertising company, what Vietnamese ??
Q: What are you talking about? What are Vietnamese? We carry out an advertising campaign in Ukraine !!!Approximately with such phrase the client from Slovakia addressed us. We demanded access to Google Analytics to analyze the situation and imagine how surprising it is, but - the client spoke on the case.
The bottom line: since January 14, Google Analytics provides geolocation statistics with an error for Ukraine.')
What do we have:
1. Glitch analytics, which meshed the grid.
2. Mass emigration of Ukrainians to Vietnam.
3. Your suggestion in the comments.
More details about the problem can be found under the cut.
Statistics of the advertising site
sinoptik.ua (included in the top 20 most visited resources of Ukraine):

At the moment, we conducted a mini-survey on Facebook (happy birthday, by the way, it’s worth congratulating), and analyzed in detail all the statistics, the result: since January 14, globally on all Ukrainian sites, we noticed a similar failure in Google Analytics. You can see this in the following graphs.
From January 1 to 15 :
From January 16 to January 31 :

If you look at the map, we can see that not only Vietnam has appeared, besides it there are other countries that have dramatically darkened, we will study further.
Ps I apologize for the humorous headline, but in our office this is the hottest topic of the day. We will hand over the report to the client and say that this is a mass emigration to Vietnam.
P.P.S. And what is the situation on your site?