From 1865 to the present, the conception of who is an American deserving of the full rights of citizenship has changed over time. Describe the expansion of who is or is not an American with consideration to historical context.

In 1865, the predominant view of who was truly American and deserving of full rights narrowly applied to white men. In the period of Reconstruction, following the Civil War, this conception drastically changed. The 14th Amendment stated that all people born in the United States were citizens. This was a distinct departure from the Dred Scott Decision in the 1850s, in which the ruling stated that blacks were not citizens. While the 14th Amendment extended citizenship and equal protection under the law to black Americans, they were still not treated as full, equal members of American society. Another Reconstruction amendment, the 15th Amendment, granted black men the right to vote. With these amendments, black Americans were legally full citizens with equal rights. In practice, however, these rights would be curtailed through loopholes restricting their ability to vote and through discriminatory segregation laws. The movement to achieve real equality reached its peak in the mid-twentieth century. In the 1960s, the Civil Rights Movement achieved significant gains with the passage of the 1964 Civil Rights Act, which prohibited segregation, and the 1965 Voting Rights Act, which put into place measures to ensure blacks were able to vote.
Another group whose citizenship and rights changed in the post–Civil War period was Native Americans. They were legally considered to be a special case of a nation within a nation. As such, they were not automatically considered citizens, even though they were born within the borders of the United States. Tribes were often forcibly removed from their land as white demand for those lands increased. In the late nineteenth century, an assimilationist movement gained popularity. The idea behind this was to “kill the Indian, but save the man.” Reformers believed that an alternative to killing Native Americans was to assimilate them into white culture. Schools were set up to assimilate Native American children. Assimilation also became a prerequisite for citizenship through the Dawes Act, passed in 1887. This practice remained in place until the 1920s when the Indian Citizenship Act extended citizenship to all Native Americans born in the country.
Women, even white women, were another group who did not enjoy full rights in 1865. While white women were considered citizens, they did not have the right to vote, and they also faced many other restrictions. For example, in many places, married women were not allowed to work or own property. Women were granted the right to vote with the 19th Amendment in 1920. Similarly to black Americans, however, this did not mark the end of women’s fight for full equality. Throughout the twentieth century, the women’s rights movement continued to push for full equality through measures such as the Equal Pay Act.
Finally, there is the case of immigrants. In its early history, America had an open immigration policy. As immigration numbers increased and anti-immigrant sentiment also increased, greater restrictions were placed on who would be allowed to immigrate to the US and how these immigrants could become citizens. In the 1880s, the Chinese Exclusion Act prohibited most Chinese people from coming to the county. In the 1920s, quotas were placed on how many people from each country could immigrate to the US. These restrictions largely remained in place until the 1960s.
https://cis.org/Historical-Overview-Immigration-Policy

The mid-1800s saw an increase in European immigration to the United States, particularly those from Ireland, Scotland, Germany, and Poland. Despite facing discrimination from Americans, they were eventually recognized as citizens of the United States. On the other hand, African Americans who have lived in the United States for many generations—many as far back as the colonial period—were still considered second-class citizens and had very limited rights. This was the case in after the conclusion of the Civil War and the Emancipation Proclamation.
It wasn't until the mid- to late-twentieth-century that African Americans were protected from voting rights violations and were integrated in the South. Later in the twentieth-century, Asian and Latin American immigrants moved to the United States en masse, mostly due to political or economic instability in their respective countries.
Unlike African Americans and Jews before them—who were considered Americans, but were discriminated against—the experiences of Asian and Hispanic immigrants were more blatantly alienating. For instance, even today many Americans of Asian-descent complain of white and black Americans asking them where they are from—meaning, what country they are from—despite being born and raised in America.
Today, there are many Asian and Latino political movements and organizations that raise awareness on the minority experience, especially on being considered non-American despite their American nationality.