To answer the question: "Clover - a symbol of what country?" Could be uniquely - Ireland. However, here it is necessary to clarify ...
The national symbol of Ireland, the Irish themselves, as well as the Irish Christianity is not just a clover as a plant, but a trefoil clover, or a shamrock.
According to legend, the most revered among the Irish, the patron saint and patron Saint Patrick revealed to the islanders, the inhabitants of Ireland, the essence of the Holy Trinity is the example of the trefoil. Therefore, a shamrock, real or artificial - an indispensable attribute of a loved one both in Ireland and outside St. Patrick's Day.
According to the constitution, three-leafed clover is the official state symbol of Ireland, it is also registered as its trademark. That does not prevent to use it as an emblem of sports clubs, universities, various state institutions and even military units. Shamrock is depicted on Irish postage stamps, used in signs of distinction in military and police uniforms.
There are examples of using trefoil as a symbol outside of Ireland. The image of a three-leafed clover is adorned on the arms of the Canadian city of Montreal, as a recognition that among its first settlers there were many Irish. The image or name of the trefoil is often used by Irish pubs (pubs) around the world.