Adding or removing a country name in text will not affect traffic adversely unless you have replaced everything with new content all about Ireland and the search terms you had were affected. For instance, if you were operating a travel advice site for the UK, and then decided to switch this to Ireland, then you could expect to see this change. Those using "uk travel advice" would no longer be coming to you, and there is a direct correlation between the search numbers and the population seeking such information.
But, as I doubt your target searchers in such a way, adding and removing mentions of countries should not affect your search traffic.
As said, I think this is about something else on your site that Google objects to.
Have you used a lot of duplicate content? Do you have advertisements and banners above the fold? Have competitors done something in the last month to place themselves above you?
When you see a decline in traffic, the first thing you should do is analyse your competition to see if there is anything they have done to increase their relevance above you. If there is nothing to see there, then it's reasonable to assume that Google has lost some faith in your site and you need to try to work out what they changed in the two weeks before and after the visible decline and try to establish what it is about your site that didn't meet the requirements implemented by that algorithm change.
Edited to add: a lot of people immediately assume that it's Google's fault for lowing their traffic, and while I am no fan of Google, this is not a sensible conclusion to immediately jump to. All webmasters are in competition with others in their field, you can change something about your site, or develop a marketing and SEO strategy to knock your competition off the top spot for something, but they will be doing the same too. Always keep an eye on your competition and assume that they are watching you in just the same way. A decline in traffic could just mean that the linking strategy they started a month ago when they found you becoming someone to compete with has finally kicked in.