It really comes down to the statistics. The unfortunate truth is that black people, for whatever reason, have more violent interactions with the police. Whether that's a product of them actually committing more crime, simply being policed harder than whites, or having an anti-authority culture or some combination is up for debate. And they're such a small part of the population, roughly 12-13% vs. roughly 65% white people that every issue gets magnified.
As for the whole black history month, etc., it's kinda complicated. The argument for it is that "every other month is white history month", which there is a grain of truth to. The argument against that sort of thing we shouldn't need a month for any specific race or culture and all of that sort of thing should be threaded throughout the regular history curriculum. It isn't just Black history month, there are also months for Native Americans and Hispanic people, though those don't get nearly as much focus in schools. Asian people also seem to be left out of these things.
The fact is that Black culture has always been kind of separate from the larger American culture, but also at the same time has a hugely disproportionate influence on it. There is also, I suspect, a pretty large component of guilt to the whole thing.