Sometimes groups are segregated because their lifestyle or appearance is not accepted by others. People are tribal and afraid of difference. That goes both ways.
'Ghettos' exist all over the world, folks living in communites with other who are 'like them'. Collections of Italians in NY, Boston, San Francisco; collections of Japanese in old SF; collections of Cubans in Miami....folks wanting to be where they can more readily buy what they are accustomed to having at home, speaking the same/similar language as others around them. Some eventually become tourist attractions (Chinatown SF, Jewish quarter of Manhattan, Greek town in Chicago, Detroit and Toronto) while others languish with lower income populations. The classic 'Irish cop' stereotype arose because of communities with similarity of occupation.
Sometimes the ghettos are artificially created by authorities, like the 120,000 Japanese rounded up and put into US internment camps during WWII, in spite of the fact that many were naturalized or native born American citizens with zero allegiance to Japan. Approximately two-thirds of the internees were US citizens!
Indoctrination fi,ms for the US public made it SEEM that the Japanese people packed up and took much of their belonging in trucks/busses to the camps, the reality is one or two suitcases of clothing were permitted. Information published in encyclopedias said, " Internees lived in uninsulated barracks furnished only with cots and coal-burning stoves." The reality was that they were given straw mats to sleep on, and bathroom facilities with zero privacy within the large rooms of toilets and showers.
The Supreme Court eventually determined that the government could not detain a U.S. citizen whose loyalty was recognized by the U.S. government. Five decades later, the US finally distributed reparation payments to about 80,000.
Asians were not the only ones targeted...at least 600,000 Italians and Italian Americans—many of them naturalized citizens—swept up in a wave of racism and persecution during World War II. Hundreds of Italian “enemy aliens” were sent to
internment camps like those Japanese Americans were forced into during the war. More than 10,000 were forced from their homes, and hundreds of thousands suffered curfews, confiscations and mass surveillance during the war. Oddly, only 11,507 people of German ancestry were interned during the war.
A military 'ghetto' was the 442nd Infantry Regiment. the 442nd Infantry Regiment was an infantry regiment of the United States Army. The regiment is best known as the most decorated in U. S. military history and as a fighting unit composed almost entirely of second-generation American soldiers of Japanese ancestry who fought in World War II.