The problem is that of differing standards.
In the USA many babies are saved by advanced medical procedures. Some are lost. In a dump like Cuba, nobody would even try to save these children, so they are not counted as "live births" who can later contribute to infant mortality.
By the way, Cuba has consistently REFUSED to permit the WHO in to verify its claims of low infant mortality. I wonder why.
Please stop touting Castro's hellhole as some kind of beacon. It is a disaster.