The U.S. tax system is less progressive than those in many other industrialized nations. European countries like Denmark and France have higher top marginal tax rates (above 50%), while the U.S. top federal rate is significantly lower. Additionally, U.S. taxes and transfers do less to reduce income inequality compared to peer countries.
Raising rates on soley the rich will make the tax system even more progressive but will probably not make public service much more generous. Raising the tax rates on everyone would probably make the tax system less progressive but might actually fund a large increase in public spending.
What matters is outcomes, and the U.S. system—compared to other developed nations—does far less to redistribute wealth or fund robust public services. Other countries raise more revenue overall (often through broader-based taxes like VAT), and they spend it more equitably. So yes, technically progressive—but practically insufficient.