US firms invested almost $18 billion in Ireland in the first six months of the year, rising 49 per cent from 2010 and putting Ireland on a par with the Netherlands, Canada and the UK.
According to a report from the American Chamber of Commerce Ireland, investment from the US has grown five fold in the past 10 years, and is now worth $190 billion - more than the US has invested in the four BRIC nations combined. It accounts for about a quarter of Ireland's gross domestic product.
Ireland is home to a number of US multinationals, with big names in technology such as HP, Microsoft, Google and Intel with operations here. There are also a number of major health sciences firms operating in Ireland, including Pfizer, Medtronic and Abbott.
These multinationals contribute significantly to Irish exports, a major driver of growth in an economy currently suffering from poor domestic demand.
But the investment isn't all one way, the chamber said. Last year, Irish companies invested $8 billion, a new record, and were responsible for supporting 120,000 jobs.
Author of the report Joseph Quinlan said the relationship between Ireland and the US was an important one.
"[Global commerce] is not about trade; it's about foreign direct investment," he said. "That's how you do global business."
Addressing concerns about redundancies at multinational firms operating in Ireland, he described it as "creative destruction". "That's how business operates," he said.
But he said foreign direct investment in the relationship between businesses in Ireland and the US was longer term.
"I can't predict how the euro zone crisis is going to play out, and I'm worried about that, unequivocally," he said. "But I'm more confident at the end of the day that investors will come to realise what we already know in this room - Ireland is different from Greece, it's different from Portugal, from a lot of other countries."
Mr Quinlan praised Ireland for the adjustment the country had made in the wake of the financial crisis and subsequent bailout of the Irish banking system. He said he was confident the EU would stay intact and the euro zone would survive the current crisis.
President of the chamber Gerard Kilcommins urged the Government to maintain the investment in education "to the maximum extent possible". He said it was the quality of educated workers available in Ireland that attracted multinationals and their investment funding, rather than simply the country's low rate of corporation tax.
