CAN-SPAM specifies that the link must be clearly marked and suggests using CSS to do so, but the link is still always going to be at the bottom of the email in the smallest font used. It only matters for those of us who know to look for it; many people just have to live with the spam because they don't know it's easy to unsubscribe.
Sometimes it's not even going to be underlined or distinguished at all (that may be a violation actually but I'm not going to take them to court over it).
There's other dark patterns too, like certain unsubscribe pages requiring you to type/paste your email in to actually complete the process. That is 100% intentional friction, like github making you type the name of a repo into the deletion form. It should also be illegal for unsubscribing.