Millions of acres? Not hardly. But a few hundred thousand acres is plenty to anxiously watch. A number of states ban foreign ownership of farmland.
You’re right; all foreign investments equals 30,000,000 acres, not just China. I couldn’t find data on how much is leased, though.
https://www.technocracy.news/foreigners-own-30-million-acres-of-prime-u-s-farmland/