Question: Panthera youngi is known from Choukoutien, northeastern China and Japan, and lived about 350,000 years ago in the Pleistocene epoch, Harington, 1969 suggested that the American lion, the Eurasian cave lion and the large Chinese "Panthera youngi" are conspecific, The American lion ("Panthera leo atrox" or "P. atrox" ) – also known as the North American lion, Naegele’s giant jaguar or American cave lion – is an extinct lion of the family Felidae, endemic to which location during the Pleistocene epoch?

Context paragraphs:
Panthera onca mesembrina: Panthera onca mesembrina,is an extinct subspecies of the jaguar that was endemic to North and South America during the Pleistocene epoch (1.8 mya–11,000 years ago).

Panthera leo spelaea: Panthera leo spelaea or P. spelaea, commonly known as the European or Eurasian cave lion, is an extinct subspecies of lion.  It is known from fossils and many examples of prehistoric art.

Pliocene: The Pliocene ( ; also Pleiocene ) Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58 million years BP.  It is the second and youngest epoch of the Neogene Period in the Cenozoic Era.  The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch.  Prior to the 2009 revision of the geologic time scale, which placed the four most recent major glaciations entirely within the Pleistocene, the Pliocene also included the Gelasian stage, which lasted from 2.588 to 1.806 million years ago, and is now included in the Pleistocene.

Panthera youngi: Panthera youngi is known from Choukoutien, northeastern China and Japan, and lived about 350,000 years ago in the Pleistocene epoch.  Fossils found in Japan were originally regarded to belong to those of tigers, but being discovered later that at least some belong to lions.  Harington, 1969 suggested that the American lion, the Eurasian cave lion and the large Chinese "Panthera youngi" are conspecific.

Late Pleistocene: The Late Pleistocene is a geochronological age of the Pleistocene Epoch and is associated with Upper Pleistocene or Tarantian stage Pleistocene series rocks.  The beginning of the stage is defined by the base of the Eemian interglacial phase before the final glacial episode of the Pleistocene 126,000 ± 5,000 years ago.  The end of the age is defined as 11,700 years ago.  The age represents the end of the Pleistocene epoch and is followed by the Holocene epoch.

Panthera leo fossilis: The Early Middle Pleistocene European cave lion is an extinct feline of the Pleistocene epoch.  It was generally considered to be an early subspecies of the lion ("Panthera leo"), and thus called "Panthera leo fossilis," but a recent test suggests that cave lions may not have been subspecies of "Panthera leo", but closely related to it.  In that case, this felid would be called "Panthera fossilis."  Some have placed it within the same species as the later cave lion, under the name "Panthera spelaea fossilis."

Panthera onca augusta: Panthera onca augusta, commonly known as the Pleistocene North American jaguar, is an extinct subspecies of the jaguar that was endemic to North and South America during the Pleistocene epoch (1.8 mya–11,000 years ago).

History of lions in Europe: Lions inhabited parts of Europe during the Holocene and even historic times and formed a subspecies called "Panthera leo europaea" .  They lived in ancient Rome, ancient Greece, southern Russia, coastal parts of Saudi Arabia, and western Asia including: Turkey, Armenia, Azerbaijan, Georgia, Iran, Afghanistan, Pakistan and India.  It is also suggested by historical and fossil evidence, that they lived in Spain, Portugal, southern parts of France, Italy, Britain and the Balkans beyond Greece.  Their diet included aurochs, red deer, tarpan, wild boar, and other herbivores.  European lions could possibly have been the last remnants of the cave lion ("Panthera leo spelaea").  However, this is considered unlikely because historic depictions of European lions show animals with prominent manes, whereas cave lions are always depicted maneless in prehistoric cave art.  It is therefore assumed that modern maned lions spread during the Holocene from Africa to Eurasia.  It is not clear if the modern lion replaced the cave lion or occupied Europe after the cave lions already had vanished.

List of extinct animals of the Philippines: The Philippines had a large and diverse group of mammalian species in the past.  They are widely distributed across the archipelago.  However, they became extinct due to several factors.  There are at least eight mammalian species that have been extinct since the Pleistocene Epoch.  A fossil species of Sirenia has been found in Palawan and was found out to be extinct since the Miocene.  But, there are also extinct deer and pig fossil remains known in the Philippines that are not yet included in this list, as well as other buffalo and small mammal species from the Pleistocene Epoch.  The Asian elephant, a species that became extinct in the 13th to 16th(?)  century, was originally transported to the Sultanate of Sulu and Maguindanao but became extinct on those areas or were transported back to Sabah for unknown reasons.  One former species, "Acerodon lucifer" is now extinct, but is now highly regarded as part of the species "Acerodon jubatus" today, thus, the species still thrives in the archipelago, but is locally extinct on the island of Panay.

American lion: The American lion ("Panthera leo atrox" or "P. atrox" ) – also known as the North American lion, Naegele’s giant jaguar or American cave lion – is an extinct lion of the family Felidae, endemic to North America during the Pleistocene epoch (340,000 to 11,000 years ago), existing for about 0.33 million years.  It has been shown by genetic analysis to be a sister lineage to the Eurasian cave lion ("Panthera leo spelaea" or "P. spelaea").  It was part of the abundant Pleistocene megafauna, a wide variety of very large mammals that lived at the time.  The most abundant remains have come from the La Brea Tar Pits.

Supporting paragraphs: Panthera youngi American lion
Answer: North America