What significant limitation does the USA impose regarding notional pooling?

The correct answer highlights that notional pooling is prohibited in the USA. Notional pooling is a cash management technique that allows companies to offset balances across multiple accounts to optimize liquidity and reduce borrowing costs. However, U.S. regulations do not allow this practice as it can lead to complications regarding income taxation, the determination of legal entity taxable income, and compliance with various banking regulations.

This prohibition mainly stems from the desire to prevent tax avoidance strategies that could arise from the aggregation of funds in a manner that blurs the lines between separate legal entities. As such, each account must be treated independently for tax purposes, which aligns with U.S. laws regarding intercompany transactions and funds management.

The other options, related to unrestricted use of multiple currency accounts, the reliance on Zero Balance Accounts (ZBAs), and barriers for intercompany loans, do not capture the specific regulatory stance of the U.S. government regarding notional pooling and are therefore not the correct response.