Again, just watch any episode of Hogan's Heroes: it was winter all six seasons on that show, and yet, all the trees were lush and green, no one's breath could be seen, the actors are sweating in their caps and coats, crickets can be heard at night, etc.

But I wouldn't generalize the entire U.S., it DOES snow quite often in the northern half of the country, not so much in the southern half.