They have played 7 times
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Ireland have won 7 times out of 7 meetings against the USA
Up to 2011, Ireland and France have contested 89 rugby matches. France have won 55 matches. Ireland have won 29 matches. There have been 5 drawn matches.
Up to 2011, England and Ireland have contested 125 rugby matches: England have won 71 matches. Ireland have won 46 matches. There have been 8 drawn matches.
Ireland has many rugby teams. However, what you are probably referring to is why there is not a Republic of Ireland and a Northern Ireland team. The reason is that, like many sports in Ireland, rugby is played on an all-Ireland basis and there one organisation that looks after it, the Irish Rugby Football Union, and so there is one international team.
Since 1882, Ireland and Wales have played 117 rugby matches: Ireland have won 47 matches. Wales have won 64 matches. There have been 6 drawn matches.
They have not won the RWC at all up to 17/09/2011
Ireland's National rugby squad doesn't have a nickname
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heaps