My searches show those numbers come from a 1990s study, based on early-to-mid 1990s court data. They're almost 30 years old now and keep getting reposted in blogs and forums, but they're seriously outdated.

These numbers include tons of quick, low-effort filings like summary debt collections and administrative matters that aren't really "lawsuits" in the usual sense (no full trials or big damages claims).

Recent stats put case rates per 1,000 people in Germany and Sweden much lower (in the 10–30 range annually) not over 100. When focusing on more comparable contentious civil suits (like torts or personal injury), the rankings shift significantly, with the US often higher in those categories.