Soft power is not just movies.
Prior to the pandemic millions of Chinese waste billions to travel to Europe to soak in the architecture, food, and culture. Today, they still waste untold billions on European fashion, cosmetics, cars, western classical music lessons, etc.
It is total nonsense to suggest only America has soft power.
Secondly, movies rely heavily on existing distribution and news infrastructure and industry pull. America controls a lot of this so the combo allows them to drain the world's top talent, promote (movie reviews heavily focus on American films) and rapidly spread their junk everywhere.