There are no standard “working hours.” Each team, including the folks in the US and elsewhere, decides what their hours is. Within that, each individual usually sets her own pattern as well. So “early” teams, have some people who work “late” and viceversa.
What counts is that you deliver on your promises.
And in order to deliver on your promises, you have to interact with your team throughout their working day. It would definitely not work to have somebody working throughout the night when the rest of the team is at work during the day.
Please, read about the context for these answers.