Who are you comparing it to? The U.S. is middle of the pack in the OECD [1].
The highest-turnout countries are Equitorial Guinea, Rwanda and Turkmenistan [2]. None are democracies.
[1] https://www.oecd-ilibrary.org/docserver/reg_glance-2009-35-e...
[2] https://worldpopulationreview.com/country-rankings/voter-tur...