Is it possible to count the citations that a paper has received in a particular country using Web of Science?
WoS allows you to look at all the papers citing a given paper P, and there is a link to "Analyze Results", where country is one of the options. (It defaults to a minimum count of 2; you'll want to drop this to 1)

For a randomly selected paper from a recent search, here's an example:



There are 11 citing papers; of these, seven have at least one US author, two at least one Czech author, etc. This would give a value of 0.64 if your original author was American, or 0.18 if they were Czech.

The obvious downside is that you need to do this for each paper P; you can't do it automatically for a hundred at once. But it's a start...



Edit: you can do this through Scopus as well. Select the paper, find citing papers, "analyse search results", and you get this:

Here, there are a total of three papers citing P, two of which have German author(s), one Austrian, etc.



With Scopus, you can do the analysis for a large group of papers, but it won't help you very much. From your initial search result, select all items using the checkbox, and click "view cited by". Then analyse search results again, and you get the stats for all papers citing one or more of the original search results. However, this won't help answer your question as to %age of papers with overseas citations - they're all bundled together and not segregated by cited paper.