Not necessarily an Irish problem. The S&P500 is dominated by 6/7 tech stocks. The sell off was started in Japan, so it just shows how interconnected financial markets are.
It just goes back to basics of portfolio management. Stock markets are riskiest, bonds next and cash least risky.
Invest only a portion of your portfolio in stock markets. To reduce risk in equities the option was to invest in indices but that dynamic is changing given the dominance of a few stocks within the s&p500.
However if there is a global sell off there's not much that can be done if you're solely invested in that asset class.