Ahahaha, sorry, really?
Regarding infrastructure, most of America seriously lacks behind most of Europe. Like, you have strong electric cables just hanging around your backyards?? And watertanks on top of your buildings?
American politics simply often emphasizes other things (arguibly having it's own benefits), mostly being against regulations, which leads to companies both being more innovative sometimes, but also selling the most useless crap overpriced at other times. Most american air-conditioning systems would simply be not allowed in europe for their high energy consumption. That's why americans are still the #1 in CO2-emission per person: People in the rest of the world are exactly (if not more) advanced than people in the US, have the same amount of air-conditioning and cars. American products just are so de-regulated and inefficient, and the infrastructure so bad and public transportation non-existent, that many americans spent much of their time in traffic jams and air conditioning has to run the whole day to work.
If you want to go to the cinema during a heat-wave in Europe, you can have the whole, perfectly air-conditioned theater, with the latest, most modern high-end sound and picture quality system all for yourself alone.
\rant
A bit off-topic, but to give the real answer to your question:
Statistically Europeans tend to spent a larger time outside than Americans, especially during summer. The concept of "summer blockbuster" is rather new here, big budget movies were traditionally released in the winter months, because during that time people spent more time insides (a movie theater qualifies as "inside"). Even untill the 90s we had to wait up until ~6 months till an american blockbuster was released in Europe, to maximize profits during the "movie-going" time of the year. Then the Internet came, and movies needed to be released around the same time worldwide to prevent piracy. That's why all those blockbuster now get released in the summer here too, but to diminishing returns. Basically cinema suddenly had to compete with going to the beach, swimming or barbecue, which it will always loose to when the weather is especially hot. Which leaves a lot of the winter free for european movie productions, that normally wouldn't be able to compete with americans marketing wise.
But now that american summers get too crowded with movies, a lot of releases move to the winter as well. Titanic, Avatar and Star Wars were immensely successfull not just in the States, but also in Europe where they basically "owned" the traditional movie-going part of the year completely on their own. Europe as a whole simply has statistically colder temperatures than the US, and as soon as the heat comes, cinema is basically dead and people go outside instead.