the US work with different timezones

Timezones solve an entirely different problem.

I think that technically, time zones may include whether-or-not DST is supported, not just the "bands". But, okay, yeah, that's semantics.

That being said, the US also doesn't entirely use daylight savings time, so @Blaze@discuss.tchncs.de's point still stands.

https://en.wikipedia.org/wiki/Daylight_saving_time_in_the_United_States

Most of the United States observes daylight saving time, the practice of setting the clock forward by one hour when there is longer daylight during the day, so that evenings have more daylight and mornings have less. Exceptions include Arizona (except for the Navajo, who do observe daylight saving time in Navajo Nation),[1] Hawaii,[2] and the overseas territories of American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the United States Virgin Islands.