Each country compiles their own numbers, using their own systems, with their own guide lines. Most are not trying to make their statistics comparable to other countries. Most are simply trying to make their government look as good as possible, and often are willing to slightly bend those numbers to achieve that goal. You should read up on Thomas Sowell's story of working for the Bureau of Labor Statistics. Or what Carter did to the US Geological survey.
In any case, once the statistics are released, organizations like the WHO, will compile those numbers, but they often do so on face value. Usually this is because they can't do anything else. The data from government controlled hospitals, to government reporting agencies, to the official statistics is questionable. But the government is obviously not going to make public raw data that could be used to contradict their own statements. So often the raw data is not published, or how that got that raw data, nor how they interpreted it to the official numbers.
So when you look at those numbers, you really don't know what went into them. If you think the statisticians are making adjustments between countries to account for differences, that's just not true. The WHO and others that compile such numbers, don't have the data to make such adjustments. The people at the government agencies, would never adjust their numbers higher for fear of being removed.
And some of the differences are quite interesting. Many have a limit on weight. If the baby is less than X weight, they are not considered alive. They are either abandoned completely, or helped, but if they die, it doesn't count. Other have a limit on time. If the baby is X weeks early, it's not alive. I have even read that some have a length limit. It must be such and such a length, or it is not counted. Some have special exceptions. Mother on crack, drunk or something, and the baby dies, that's not counted.
Then there are some systems where the incentives are such, that doctors simply don't report it. If they report a baby died, they could get into trouble. So instead, they just don't report it. This is the case in Cuba and a few other countries.
Another common problem is the sill-born loophole. Many countries, if the child dies within 24 hours of birth, they call it a still born. The reason of course is that a still born is not considered a live birth, and thus isn't reported on the infant mortality. Many suspect that Japan and a few others do this.
By the way, this is why survival rates are such good measurements. You either have cancer or you don't. You don't "sort of" have cancer. It's either yes or no. There's not much wiggle room there. Then you are either alive or dead in 5 years. Five years after you got the cancer, you are either in the ground, or alive and kicking. That's all there is too it. And of course, we rock on survival rates, and lead the world.
The Bottom line is, it seems like you need more justification to accept those infant mortality rates, than I do to dismiss them.
And we haven't even talked about the causes yet. Infant mortality isn't simply about an infant in a hospital. If your a crack whore, and pop out a kid, and take him home where your pimp ends up killing it, that's infant mortality, and has nothing at all to do with the health care system.
Nor do most of the other causes of infant death. For example obese mothers tend to have more risky pregnancies. Of course, being on drugs, or drinking alcohol, even smoking can cause you have a high risk birth. All of these are things the hospital couldn't possibly prevent.