Yup, the majority of people experiencing this issue are AT&T customers, but not all of them. A lot of other ISPs will use AT&T's network and are routed to the same NTT node.

You can see the megathread here. Also if you wanna see where you're having issues, you can look at a post made last year about similar issues. Instructions on how/where to do a traceroute are in the post.

Also, if you post your traceroute, make sure to remove/blur the first couple of returns for your privacy.