As you said, "race" was invented a few centuries ago to justify the chattel enslavement of African people. Although a social construct, it had just as much meaning as that other social construct, "money." The wealth of the USA was built on the unpaid labor of enslaved Black people. Even the US capitol was built on stolen labor.

Remember the Southern strategy? "If you can get the lowest white man to think he's better than the best-colored man, he won't care if you pick his pockets. Hell, give him someone to look down on, and he'll gladly hand over his wallet" -- former president LB Johnson. Until a few decades ago, there was an unspoken promise to Southern white folks: no matter how bad things get, you'll always be better off than the Black people on the other side of town. White people felt threatened by the Civil Rights movement because they saw that this promise would soon be broken. The deal was sealed when Obama was elected president, and the Tea Party was born. Now, we have a wannabe dictator running for president on a platform of white grievance. If he's elected, God help us all.

Your message applies well to personal racism, aka bigotry. However, it does not address systemic racism. If you don't know the difference, please educate yourself. This article is a good start.