Carthage defeats Rome in the Second Punic War (probably by Hannibal linking with Hasdrubal or Mago, defeating another Roman Army and besieging and taking Rome).
Rome and its culture is destroyed utterly. The city is burned and its people sold into slavery. Many of the important ones are sacrificed in Carthage.
Carthage fights a civil war between republican factions and the supporters of the Barcas. The Barcists win and establish the family as Kings of Carthage.
The son of Hannibal, before fighting a major battle, sacrifices his own son to the gods after receiving a vision (likely brought on by hallucinogenic drugs) that this would give him victory. He wins the battle and establishes human sacrifice as a major tenet of Carthaginian identity.
Carthage expands across the Mediterranean, establishing an empire from Iberia to Mesopotamia and from the Loire to the Blue Nile.
Carthaginian and Phoenician/Canaanite paganism becomes very popular around the Mediterranean, along with its practices of human sacrifice. In the east, Babylonian and Egyptian paganism experiences a revival.
North of Carthage, the tribes of Gaul and Britannia develop as unconquered societies, and the tribes of Germania grow to become settled kingdoms by the fourth century AD. Their religious practices involving human sacrifice expand and are developed upon. When the Huns and Vandals come onto the scene later on, they drive the Germans and Gauls westward and southwards into Carthage.
After the Fall of Carthage in the 6th century, the religions of the Celts, Germans, Huns, and Carthaginians mix into a variety of interesting ideas and mysticisms, all heavily involving human sacrifice. Specifically of infants and the citizens of captured cities.
In the 900s-1100s AD, a major nomadic power from central asia invades and conquers much of the middle east, which practices human sacrifice extensively. This serves as a catalyst for the spread of a major new religion...
During a major famine after a drought and a major storm of locusts ravage the region, a prophet from the revived city of Babylon preaches an insane mixture of Zoroastrianism, Canaanite paganism, and Carthaginian religion, which features a Duotheistic cosmology in which two gods, a god of prosperity and a god of pestilence, are engaged in an eternal war with armies of spirits and demons. In order to help the god of prosperity to win, man must sacrifice infants and virgins regularly and in a certain way. The eschatology involves an orgy of slaughter in the final days which results in the victory of prosperity and heaven on earth.
This religion spreads like Islam over the old world, carried by the army of the prophet, as well as by pollination from nomadic conquerors.
Meanwhile in the Americas, the Aztec and Maya civilizations develop. The Aztecs continue expanding in the Valley of Mexico without European invasion, eventually coming to rule a relatively vast territory from OTL Sinaloa to Guatemala. Over time, Aztec government coalesces into a unitary imperial system ruled from Tenochtitlan.
A King of the Maya in OTL Tabasco, who is a genius military commander experienced from fighting the Mextec tribes, militarily unifies the Maya states for the first time. His Maya Empire, centered on Tabasco, and containing Mextec lands, adopts many Aztec practices through cultural contact. The Maya Empire fractures again after his death, but the idea of a unified Maya does not, and warlords now aim always to conquer the whole of the Yucatan.
After a while, the Aztec Empire and the dynasties which come to rule a Maya Empire grow to dominate together OTL Mexico. The Maya even develop a naval tradition which helps them to establish colonies around the gulf of Mexico which boom and bust and serve as a pressure valve for the fluctuating agricultural benefit of the Yucatan.
Both the Aztec and Maya religions feature human sacrifice heavily, and upon contact with the states of post-Carthage Europe in the 18th century, instead of conquest as OTL, trade relationships and cultural exchange develop...
There you have the beginnings of a world of human sacrifice
