AVERAGEIFS gives me two different results in two tables that have same values

I see no total line on your tables with this average calculation - where exactly will I find 63 and 59 respectively???

If I understand what is going on, in Tab 1, you are compiling averages based on category and country, then averaging those results to get an overall average (63). In Tab 2, you have all of the raw data, and you are taking an average from this table of all the category B data, independent of country (the 59).

I'm not enough of a statistician to justify either practice, but I do know that an average of averages is not the same thing as the overall average of the raw data. That is the difference between the two results. I know of no way to force an average of averages to be the same as the average of raw. You can look at the algebra of the average function and determine under what data conditions the average of averages will be identical to the average of raw, but those conditions are fairly specific.

Assuming I understand, you need to come up with a statistical justification for which result you believe is most correct. If you are uncertain, the standard rule of thumb is to always prefer average of raw over an average of averages, but, as with any rule of thumb, there will be exceptions.

In short -- default to rejecting the average of averages unless you have specific reasons for believing it is more appropriate.

Average = sum/number of incidents

Take a look at the 2 pivots I made from both tab 1 + 2

I made a SUM column + COUNT + AVERAGE column for both
so though the Average column is identical by line in both - see that the sum /count are different. If you calculate manually by diving SUM/COUNT for each you will get 2 different results which you mention in your post...