USD in bank accounts is definitely fungible. They may track who sends what money to whom. But this transaction data is not tied to specific 'dollars' just to 'dollars' in general. So yes, perfectly fungible.
1. Spending dollars on US soil from an US bank account won't incur extra fees (at least visible to the person - I know about interchange fees, but they are borne by the merchant), while using card issued by a foreign bank can incur fees for cross-border transactions (at the level of 2-3% usually).
2. Sanctions and KYC concerns also make different dollars have different value. Money in US bank account of an US company employee can be used at face value - money in some less-favored country bank, not so much.