In all parts of Ireland except Northern Ireland, the power system is the same as in most of Continental Europe - 220 volts, 50 hertz. In Northern Ireland and Britain, the electricity supply is of a slightly higher voltage - 240 volts. The slight difference between the two can be ignored for most practical purposes for equipment designed for either voltage.
However, the difference in voltage between the U.S.A and Europe (110 volts versus 220 volts) is a more serious problem. Connecting equipment such as hairdryers etc., designed for 110v to a 220v supply is likely to have undesirable or dangerous consequences. Heating equipment will produce 3 - 4 times more heat than at 110v. The extreme temperature will very likely damage or shorten the life of the heating elements. Lighting equipment would produce much more light at 220v, but will blow in a very short time.
Electronic equipment designed for 110v would be seriously damaged by being run at twice its design voltage. The exception is some sophisticated modern electronic equipment, such as laptop computers, which are designed to automatically adapt to different supply voltages.