One thing that makes comparing numbers more challenging is who is defined as homeless in the counts. I'm not sure where your Paris numbers are from, I couldn't find them in the source link. The SF numbers are a PIT count + shelter population for a specific night in January.

Paris homeless point in time count of 4,227 in January 2024 [1] France for individuals living rough 141,500 [2]

[1] https://www.sortiraparis.com/en/news/in-paris/articles/24790....

[2] https://redcross.eu/projects/mobile-teams-assisting-homeless...