The issue at hand is people dont understand Race,Ethnicity, and Nationality.
"We" are all Black, Black Race has tons of different ethnic group, and a Black Person could be from different Nations.
Black people are the only ones who were victims of the Transatlantic slave trade thus we cannot use the same "guidelines" as other groups when it comes to describing ourselves as no other group has had a disruption of the magnitude as black people (specifically those of West African ancestry).
That said, Black Americans relate to each other no matter their ethnicity, a Black kid with Jamaican parents that was born in Harlem will relate to an AA more than he would a Black kid born in Kingston, because even if his parents passes down Jamaican culture, that child is still a Black American and takes on the issues other Black Americans face.
The issue with Immigrants is that they were born into one culture and moved to another culture and think they are a Black Jamaican living in America thus the issues of Black America does not impact them which is false. So while the immigrant may not understand the cause of the issues in the land they are in, it would be wise to honor what is happening because the same way a Black Jamaican can criticize Black Americas (in particular AAs) about why they have issues, a Black American can look at the state of Jamaican and make the same criticism.
The issue globally is white supremacy had created the narrative in every nation that the black natives there brought their issues on themselves, and people who immigrate to these lands think of it as being fact since these narratives are typically the only introduction and knowledge they have of people from those nations.