Higher voltage allows for lower amperage for given watts / more wattage at a given amper limit. The higher the amperage, the larger the wires need to be to avoi

Higher voltage allows for lower amperage for given watts / more wattage at a given amper limit. The higher the amperage, the larger the wires need to be to avoid excess heat. In the US, standard household circuits are rated for 15 or 20 amps, in the EU 10 and 16 are common. So, you can expect a 3.5kW AC unit to work without problems in the EU while getting anything more than 2kW in North America is a serious headache.