Consider the problems of owning real estate....
- It's immobile, so it cannot be removed & taken elsewhere.
- It's subject to local, state, & federal government regulation,
ie, control over what can be done with it.
- It's subject to a lot of taxation. Even if it's unproductive
(ie, unprofitable), there are still real estate taxes.
- If China wages war against us, it can be seized.
Now.....where's China's economic threat?
Obviously, it's not their having property here.
It's that US companies have property in China.
It depends on the type of land.
We've had substantial investment here in mining, farming and major infrastructure (ie. airports and ports) which becomes a larger question than 'just' land, and relates directly to control over revenue producing industries.
I agree that Chinese ownership of tenement blocks doesn't seem problematic in isolation.