It's not an artifact of division necessarily -- it's that the US government, structurally, has an extraordinarily high number of veto points.

eg in federal legislation: the House (majority); the Senate, representing increasingly tiny numbers of Americans (supermajority, often: cloture); the president, and the supreme court.

Ezra Klein wrote a book about it. https://simonandschusterpublishing.com/why-were-polarized/