Even though the US allows copyright assignment, none of the Big Five publishing houses in the US require it as part of a standard book deal, even with first-time authors. If you open any book or ebook to the copyright page, unless it's something like a reference book (which are frequently work-for-hire), it will say some variant of "© Author's Name."

Publishers get exclusive print publishing rights for a given market, typically get digital and audio publication rights for the same, and frequently get a handful of other rights like the ability to license it for publication in other markets. But ownership of the work is almost always retained by the author.