When a country became too powerful, it easily found itself jointly targeted by other nations. Germany and Soviet Union were both in similar situations, as were Spain, France, and the Holy Roman Empire in the past...
The United States and East Africa were exceptions because their geographical positions were rather unique.
The United States stood unrivaled in North America, and East Africa in Africa. Calling them the "elders of their respective continents" would not be an exaggeration. They had few neighboring countries, and those neighbors were small, so the nations around them could basically lie flat.
As for countries beyond North America and Africa, it was difficult for them to cross the seas and unite against nations like the United States and East Africa. On the other hand, precisely because those two nations stood isolated overseas, other countries did not feel overwhelming psychological pressure from them.
Lithuania from his previous life offered a reference point. It could hide in the heart of the European continent and, sheltered by the favoritism and protection of the European Union and NATO, freely provoke the Far East Empire.
By the same logic, if the vassal states around Germany showed disrespect toward East Africa now, East Africa would not be able to do much to that country in the short term.
In short, superpowers like the United States and East Africa enjoyed greatly enhanced security because of their geographical positions, but those positions also restricted their dealings with other countries and diminished their power of deterrence.
The situation on the European continent was completely different. Germany's strength would stir unease in Western Europe, Northern Europe, and Eastern Europe. Even within Germany's own sphere of influence, there were worries about Germany. Poland, for instance, had to consider whether Germany might swallow Poland whole, bones and all.