Yonah Freemark (Twitter) is a PhD student at MIT and author of The Transport Politic, probably one of the most widely read websites in the field of transportation research and policy. Yonah has recently published a very great piece looking at the trends of public transport ridership between 2002 and 2018 for the 30 largest urban areas in the USA and France. This is the general outlook:
"Between 2002 and 2010, both countries saw increases in transit use in their major cities. The average U.S. city’s ridership increased by 6 percent over that time (though the peak was in 2008). [...]. This trend has diverged dramatically since the Great Recession, however. While the average French urban region saw its ridership increase by 32 percent between 2010 and 2018, U.S. regions saw ridership decline by 6 percent on average."
The piece is interesting throughout, with a nuanced analysis of what could explain the success and failure of French and American cities in building public transport ridership. Highly recommended.