Sometimes, apps that are made in other countries never make it out of that country. This means that the app is only used in that one particular country. It hasn’t spread to other countries. The same can be said for WeChat in the United States.
Usually, only people who live in the United States and communicate with people in Asia consistently may use WeChat. Otherwise, the people in the United States seem to use apps that were created in the United States. They are more familiar with those apps.
Also, if there are issues, they would have to call and get an English speaker. There are some issues too. To access WeChat, you really need someone else to help you begin and create your own account.