The States span from UTC-5 to -10. While the east coast is getting off work Hawaii is taking lunch. There's no way to have a single zone work for the whole country.

So how do we deal?

Well pretty much everything is just referred to in local time. TV shows are scheduled in local time, concerts and events are in local time, meetings with friends are in local time. Quite often this is a non issue. The time zone bands are multiple states wide, so day to day stuff is just..."normal."

What about when it's not?

If you work across time zones your meetings may be scheduled for your team and not you. I have an extra clock on my work computer that helps me keep track with my team, but I also just implicitly adjust times by 2 hours when talking with them.

If you regularly communicate with friends in a different zone you just need to be cognizant of when they get off work--that could be "they get off at 6pm (my local)" or "oh yeah, they're an hour behind, so I'll do some chores first."

If you have to cross into a different zone for a scheduled event. This is probably the most tricky one, especially if you live near a different zone. I find this one the most difficult as the majority of things you'd get a reservation for are handled in local time, so most concerts, restaurant, sports events, you attend will be the time you use throughout the day, but sometimes you end up driving an hour west for a timed entry event and just happen to forget that part of Florida's panhandle does things wrong and you end up arriving at the improper time,

The most common thing to get a little confused about is major televised events like the NYC ball drop, Thanksgiving Day Parade, Inauguration, or the Superbowl. Even so, these are either a set time every occurrence (and you just learn that the ball drops at 10pm instead of midnight) or are advertised at local time (and you have an early or late dinner for your superbowl party).

I know where my friends and family live, and I know where I work. I just have those offsets memorized (like we used to have phone numbers memorized). Given that, I don't really keep a separate clock for personal use and I don't really have to look up the time for anyone.

Finally, the vast majority of the US population lives in either PST or EST zones or Texas (CST) so most people are living their life really only caring about 1 or 2 timezones with any regularity.