I found this online, but I was thinking that would only apply if I had used to euros to acquire the US dollar share, whereas I've been given them in Dollars.
Foreign exchange – the basic rule here is that CGT is calculated using euro (equivalent) values at the time of acquisition & disposal. This means that if there is a fx movement, then it will be included in the Irish tax computation.
An ever more popular topic in this era of low interest rates. Here is a list of some interesting enough tax points for client share investments. Relevant for Irish tax resident individuals and skips the basics