The vast majority of these assets are in Europe.
The EU has even greater asset totals in Russia.
If there were US/EU seizure of assets, my recall is the loss of EU assets would exceed those seized.
Then there are the joint production agreements for Russian oil and gas fields. Companies have abandoned activities, but the retain the contractual rights to X% of production.
The same is true of other industries. Companies bought % interest in many businesses, sought to sell as part of existing, but in most cases could not get a good price so the still retain those assets.
In Russia.
And for far more than $300B.
What will happen is these companies will sue the US for forcing loss of those assets. We will still wind up paying for them.