Mr Cameron is expected to set out plans to renegotiate his country's relationship with Europe, which will then be the subject of a British referendum, probably in 2018.
He is under pressure from within his own Tory party, with some calling for British renegotiation or even withdrawal.
But Mr Kenny hinted that any moves to renegotiate EU treaties could lead to more referendums in Ireland.
"I think it would be catastrophic if Britain were to leave the European Union," the Taoiseach said, adding that most new treaties were subject to referendums in Ireland.
"I cannot see renegotiations for any country in the time ahead. We're going to have European elections next year, a new commission and it may well be that down the road, in the context of deeper integration of Europe, we may well have to have further treaties."
"I genuinely believe, while it will take some time to do this, the consequence of doing a deal between Europe and the United States would be phenomenal in terms of all economies and has the potential to rise them by 2pc on average," he said.
European Parliament president Martin Schulz also said he didn't think it would be "realistic" to renegotiate existing EU treaties. Mr Schulz again supported Irish demands for a deal on our bank debt, saying the Irish taxpayer had protected the European banking system and prevented "contagion".
Earlier, Mr Kenny told MEPs the worst of the economic crisis may be over.
"I believe that in 2012 we saw the passing of possibly the worst of the economic crisis – the fear that the euro itself might not survive was confronted and dispelled emphatically and we now move on to the challenges of the recovery of Europe."
However, he risks repeating the mistake of the late Brian Lenihan, who declared in December 2009: "The worst is over, we have turned the corner."
Mr Kenny also said Ireland was determined to exit the bailout by the end of the year, and that the Government wanted agreement on the EU budget before the country's six-month EU presidency ends.