France has much lower per capita debt and deficit compared to the United States. I find it very funny to hear American media talk about the dire situation of French public finances.
They can because the USD is the world's reserve currency. Whenever the economic situation looks volatile, historically, organisations buy up USD and Treasuries as a its seen as a safe haven. That trust has been slowly eroding only due to the actions (and inaction) of the US admin regarding ukraine and iran