Actually it’s mostly due to the construction materials and techniques used. American houses are generally less well insulated and built with the explicit expectation that there will be active air conditioning used to maintain the temperature.
Meanwhile in Europe this is not only comparatively very expensive to do, it is also largely unnecessary due to many buildings predating modern air conditioning, using good insulation and passive systems to maintain a comfortable temperature. There are also regulations on newly built houses that make it generally attractive to build energy efficient.