From an interesting report comparing GDP of countries against gross metropolitan product of the large cities in the US ($$s in billions):
Rank Country or Metro Area 2010
1 United States 14,660.4
2 China 5,877.2
3 Japan 5,462.6
4 Germany 3,297.7
5 France 2,554.5
6 United Kingdom 2,241.9
7 Brazil 2,088.0
8 Italy 2,046.9
9 India 1,607.6
10 Canada 1,574.1
11 Russia 1,479.3
12 Spain 1,405.4
13 New York-Northern New Jersey-Long Island, NY-NJ-PA 1,282.6
14 Australia 1,232.5
15 Mexico 1,040.1
Ireland ranks 56th on the list, below NY, LA, Chicago, Washington DC, Houston, Dallas, Philadelphia, San Francisco, Boston, Atlanta, Miami, and Seattle, and just above Minneapolis and Detroit. Here's a map showing how some countries compare, via the Atlantic: