Those Americans who call themselves African-Americans rarely have 100% African genes. Many of them have over 50% European genes.
25% of Americans have Irish ancestry.
10% of those, are African-Americans.
The genes that determine physical appearance are often inherited in a way so that a dominant characteristic trumps other genes. That is why the primarily Caucasian population of China has almond shaped eyes with an epicanthic fold. It is why the primarily Caucasian African-Americans have brown skin, curly hair, fuller lips and butts.
The fact is that there is no such thing as race. Only genes that have become common in certain areas due to lack of travel and interaction. However, in the modern world there is so much travel and interaction, that this is changing. Already, a racial type that looks middle eastern is arising the US black population, the same way it originally arose in the Middle East from African people interbreeding with Asian people. Cauc-Asian people. Remember that until 12,000 years ago, Europe was under several kilometers of ice. The Cauc-Asian people lived in central asia.
We are all blended and blending is natural. Nothing can stop what is coming, which is an increasingly blended and varied population. There will still be people who appear pure white or very African. But it will be more common for two white people to have a brown skinned curly–haired child. Or two black people to have a pale tan skinned, straight haired child.