In the United States, especially among Americans, many people do not reply to texts or messages immediately; even work-related messages (Teams, Slack), many people do not reply instantly: for important matters, many take time to think about how to respond thoroughly before replying; for unimportant matters, some forget altogether. Additionally, in the U.S., looking at your phone when meeting, gathering, or communicating with others (such as in meetings, dining, or having coffee) is considered impolite; family time is also respected by not looking at phones. Therefore, many people set aside a certain time each day to respond to texts or other messages, then put their phones down; so even very close friends might only reply after dinner the next day.

Many people treat their elderly parents, seniors, and superiors the same way. Over time, in the U.S., not replying immediately has become a social etiquette. But people who dislike replying or reply slowly often show warmth when meeting in person. Therefore, in the U.S., for important matters, I usually call the other person directly rather than send a text; sending a text means not expecting a quick reply.
However, Chinese people tend to reply instantly, and instant replying is even a Chinese custom, which is an interesting social etiquette. Several times, friends from China came to travel, old classmates they hadn’t seen in over ten years, yet they constantly looked at their phones; they said that even when on business trips or traveling abroad, they need to reply at any moment.
But Chinese people who have stayed in the U.S. for a long time also gradually stop replying instantly and no longer expect quick responses from others. The differences in feelings and psychological boundaries between Chinese and Western people, along with many cultural details reflected in these differences, are very interesting.