I hope that I understood your request correctly. This can be solved, but it will require a data island and a calculated dimension, which can be quite heavy on performance in case your data set is large (millions of rows).
1. You will have to expand the country dimension to two lines (groups for items 1+2 and 3+4). Then add a second dimension that will be used for stacking.
The easiest way how to do this is by creating a data island in the script, e.g.:
load * inline [
2. Add the first dimension to the bar chart as a calculated one:
=[Country] &' - '& [group]
3. Add the second dimension to the bar chart = item (from the data island)
4. Add the conditional expression that will sum the correct field based on the "item" field value:
=pick([item],sum([Item 1]),sum([Item 2]),sum([Item 3]),sum([Item 4]))
When you color the chart by the "item" dimension, it should look something like the attached picture.
Hope this helps. Regards,