If we’re very precise (and that helps to understand the difference), it’s not applied in the same way - or on the same level - though.
You do (so far) not get Swiss tax credit for the dividends from US stocks paid to the fund.
You receive tax credit for (up to) the 15% withheld from the U.S. fund’s distribution to you.
The key difference is that the U.S. fund will receive dividends from U.S. stocks in full (unlike the Irish fund, which will only receive 85% of them, after deduction of WHT). The withholding tax will be withheld on a different level - namely when the U.S. fund distributes to the individual investor.