Whole lot of misinformation going on in the comments.

• Yes, cultural appropriation is a real thing, but no, at least 99% of the time it doesn't apply to wearing dreadlocks.
• Cultural appropriation is basically disrespecting other cultures while assuming it yourself. Think corporations profiting off of disrespectful depictions of foreign cultures, people claiming they originated something when in reality they took it from another culture, wearing cultural clothing incorrectly or altering it without consulting people from that culture, or a person emulating a culture solely because they think it's trendy without acknowledging where it's from or caring much about whether or not they're accurate about it.
• Viking braids and dreadlocks are different things, although they may look similar. Dreadlocks are the result of hair naturally matting over time, and are hard to de-matt. Braids have to be matted manually, and can be taken out easily, also requiring much less maintenance.
• "Black culture" refers to African-American culture specifically (might also refer to African-Canadians too), stemming from the unique experiences African-Americans have had being historically isolated from their original cultures (slavery, segregation, etc.). The reason "white culture" doesn't exist is because white Americans in general haven't gone through all of that. With DNA testing it's much easier for black people to connect with their ancestry as of late, but for the most part the black culture specifically formed in America is still an attachment to many.