In a country the size of the United States, it is always a good time to visit somewhere, especially if we take into account that Alaska, Hawaii and American Samoa, among other territories, are part of the country.
With regard to the continental USA, the seasons are equivalent to those in Europe, but far from being simultaneous to all the states of the country, with substantial differences caused by latitude, altitude and orography, exposure to the oceans, among other factors. In Florida, for example, it's rarely serious winter. In certain sections of the Rocky Mountains, winter almost doesn't come until June.
Anyway, unless the reason for your trip is the snow sports, in general, a time of year to visit most of the country is summer, mid-May in mid-September but bear in mind that the areas closest to the deserts at that time have very high temperatures, easily ranging from 35ºC to 45ºC for most of the day.
A certain variable period of autumn brings landscapes with yellow foliage of great beauty to various forested areas.