Hi Ash,
I hope this information is of assistance and will help to explain your rights. Prior to the implementation of the Montreal Convention 1999 and it's subsequent entry into force, the issue of airline liability internationally was subject to a complex number of liability regimes.
You and other readers may be familiar with some of these regimes for example, the Warsaw Convention 1929 and it's amending instrumentes and the EU Regulations of 1997 and 2002. The reason I make reference to both of these systems of liability regimes is they have an important bearing on how policy has been developed and implemented today.
The Montreal Convention 1999 introduces a number of new features - I won't go ito all of them today - save what refers to your question.
Article 22.1 of the Montreal Convention 1999 sets down the rules regarding damage caused by delay to passengers of 4,150 Special Drawing Rights (or SDR's). Today's (24 August 2005) IMF valuation for 4,150 SDRs is (approx 4,952 euro).
While many passengers suffer delay when flying, it's unusual for compensable damage to occur. Normal airline practice is to make provision for delayed passengers by way of subsistence and where necessary, overnight accommodation. The limit of 4,150 SDRs is probably sufficient to cover situations where an airline fails to do this in the event of delay. This limit may however be insufficient to cover the payment of significant resulting damages (such as a missed holiday) but these matters are normally covered by your travel isnurance.
Importantly, an airline is liable for passenger delays unless it, it's servants and agents took all reasonable measures to avoid the damage or it was impossible to take such measures. Incidentally, liability for passenger delays by EU air carriers under EU Regulations is governed by the same principles.
I suggest you bear the following in mind in considering whether to take this matter further. (I am playing devils advocate in relation to some of them but they should help claify the matter for you):
(a) Did the airline, its servants or agents do all in their power to avoid the damage
resulting in your delay?
(b) Are ATC (air traffic control) delays something the airline reasonably tried to avoid
or could reasonably prevent?
(c) What is/was the airline's normal practice in relation to delayed passengers and was
this procedure followed through in your experience?
(d) Article 1 (3) of Montreal Convention 1999 states that carriage to be performed by
several different carriers is to be undivided carriage if it has been agreed by the
parties as a single operation. Given you purchased a 'through ticket' from a single
carrier, my feeling is your dispute is with the US carrier form whom you purchased
the ticket.
(e) Given increased security checks at US and other airports did you leave enough
time between flights to cover any possible delays? You say the flight from KC to
Chicago was delayed by over 1 hour and when you arrived in Chicago your flight
was leaving. Should you have left more time than this between flights to take
account of any possible delays?
You didn't indicate in your question whether the carrier from Chicago to Dublin was an Irish air carrier. From what you have said, I don't believe the carrier from Chicago to Dublin was at fault anyway. As you arrived late in Chicago, the carrier from Chicago to Dublin was not obliged to allow you to board, since part of your contract of carriage with the Chicago-Dublin carrier involves presenting yourself on time for check-in.
Unless you can prove that the airline from KC to Chicago failed to reasonably avoid the delay or could reasonably expected to have prevented it, or the airline did not fulfil it's normal practice in terms of making provision for you - I think you you may have difficulty proving your case.
You don't have any claim under EU regulations if carrier was from the US in any event.
If you are still interested in pursuing your claim against this carrier - I would suggest you obtain legal advice from someone with expertise in Aviation Law and knowledge of precedent through the Courts in Ireland. There are a number of firms who deal with aviation-related matters but shop around and obtain some quotes for fees before you decide on a legal advisor.
Rgarding your insurance policy issues - you should again read the terms of your insurance policy (in the light of above) to see what the restrictions are/if any regarding passenger delays. Remember - you may refer your claim regarding insurance providers in Ireland to the Insurance Ombudsman ([broken link removed]).
I realise this area of aviation law is complex and it's hard to find out detailed information. I hope this is of assistance however.