Looking at the numbers, it seems French household debt to income has actually surpassed American (both around the 100% of disposable income) in just the last few years. French ratios have been gradually increasing for the last 25 years and American has been falling for the last decade.

One factor is Americans have significantly higher disposable income and can service more debt.

https://data.oecd.org/hha/household-debt.htm#indicator-chart