If the US ETFs I'm interested already have low yield dividends, are Irish domiciled stocks still worth it?

In general, yes.

For example, taking two popular ETF that tracks the S&P500 index, VOO vs. VUSD. While the expense ratio of Ireland-domiciled VUSD's 0.07% is higher than US-domiciled VOO's 0.03%, the higher dividend yield (after taxes) of VUSD's 1.31% would be more than enough to make up for VOO's dividend yield of 1.06%.

However, let's look at another popular ETF that tracks the Nasdaq 100, QQQ vs EQQQ. Here the expense ratios are 0.20% vs 0.30% respectively, and their dividend yields are 0.38% and 0.39% respectively. In this case, it might not be worth to hold the Ireland-domiciled counterpart.

Rule of thumb here to determine if it is worth or not thus depends on the expense ratio and the dividend yield. In general, if the expense ratio is up a lot more for a Ireland-domiciled ETF that already has low dividend yield, then not much point to hold the Ireland-domiciled counterpart.

Cheers! :)

- Jeffrey (jeffreyleezq.com)

For world & S&p500 etfs yes, it's worth it. For nasdaq100 etfs, go with qqqm instead for even lower expense.