I have multilevel data that is dyadic in the unit of observation. The dyad is a unique pair of countries that sign a treaty, such that no dyad repeats itself. For example, the US-UK treaty, the US-Canada treaty, the US-Mexico treaty, and so forth (Mexico-Canada, Mexico-Panama, Mexico-Belgium and so forth are also unique dyads).
Each treaty is coded on an interval variable Y that is the dependent variable of interest. The regression model has some variables that are specific to the dyad (e.g. difference in economic power), some variables are specific to only individual members of the dyad (e.g. level of democracy in a country).
Existing studies of this dataset pool all the observations together and run regression analyses. However, I am interested in whether there are significant differences in the mean of Y across countries. Thus, I would like to analyze differences across clusters, where the cluster is the country.
My question is, given that dyadic nature of the observations, can I conduct cluster analysis for individual countries?