You’d probably be interested in the book “How democracies die” by two Harvard political scientists. They walk through the warning signs of a failing democracy and how many others have collapsed - and the answer is actually yes, there are plenty of warning signs that American democracy in particular is in trouble.
Some of the evidence they walk through: the collapse of political norms, political restraint and the rise of win at all costs brinksmanship, the delegitimization and dehumanization of political rivals, attacks against independent institutions and neutral arbiters, and much more.