Consider that China committed troops to support North Vietnam's fight in South Vietnam for decades. Yet after they won their war against South Vietnam, relations soured into a war in 1979, and relations remain bad:
Vietnam on Monday accused a Chinese vessel of firing on one of its fishing boats in disputed waters, denouncing the incident as a "serious violation" of its territorial sovereignty.
The Vietnamese boat was fishing near the contested Paracel Islands last Wednesday when it was "chased and shot at by a Chinese vessel, causing a fire in the cabin," foreign ministry spokesman Luong Thanh Nghi said.
And then there is Burma (Myanmyar) which counted China as its only friend for many decades. What were the fruits of that support?
The skirmishing (between troops and tribal rebels) on the Chinese border has ended. But the further you go into Burma the more anti-Chinese sentiment you find. Even the military is angry, accusing the Chinese of selling them second-rate and often defective weapons. Tribal people are angry at the seizure of their land (by corrupt military and political officials) for Chinese dams and pipelines, while non-tribal Burmese (the majority of the population) are angry at what they feel is exploitation by arrogant Chinese (aided by corrupt Burmese officials and businessmen).
Russia has seen former "allies" and even former parts of the Soviet Union itself join NATO and otherwise seek American friendship and protection.
And China can't make a friend to save its life, it seems. Of course they worry that North Korea could become an American ally if the current North Korean regime collapses. Look at the track record!
And let's not forget Germany, Japan, and Italy, after World War II. Or Canada and Mexico. Or Britain, for that matter. Not even the French, for all I complain about the quality of their friendship, have become an enemy. Seriously, our State Department may seem to be in desperate need of an "American desk" at times, but they have great material to work with, when you think about it. How could they not do well enough?
One day, people really have to explain how we are so awful and the source of the world's problems. ("Why do they hate us?", anyone?) We can't even get our enemies to work up a good and permanent hate against us. China and Russia have trouble keeping isolated rogues in line.