Area of the USSR is actually the sum of Russian area in Europe and areas of other European Soviet counries without the European part of Kazakhstan. I could not find data for that area nowhere.
Wasn't (and isn't) Romania (238,391 km2) bigger than GB (209,331 km2 +14,130 km2 for Northern Ireland + little for Gibraltar and all the islands)? Or the islands make the difference?
Almost. I did some reaserch because of your comment. According to Wikipedia, the areas of GB and NI is just like you wrote. But the sum of the areas of other islands is not so small. I summed up the areas of the largest islands and it is about the same size like the Northern Ireland's area. Probablly the rest is the sum of areas of other territories and small islands in Europe. The area I took is form Wiki article and as I wrote it is 242,495 square kilometers. I also found the area of the other overseas territories in other Wiki article, and together with those territories the sum of the areas is larger than 250.000 square kilometers.