Before any visit to the United States, Europeans should be shown the map below, which accurately shows the relative position of the US and Europe on the earth:
This is why it will be much hotter than you expected. This is why there will be air-conditioning everywhere. It's because just about everywhere in the US is a hell of a lot hotter than where you come from, for a much longer during the year. And because the US is rich enough to afford air-conditioning.
Simply accept these facts, and you'll have a fine old time!