Why does the mobile phone automatically send a message to an American number?

Maybe I visited some websites or leaked personal information when I was in the app.

This kind of overseas information generally belongs to telephone fraud or telephone sales.

In this case, prevention is the main thing, and you can download a software to prevent strange calls from being intercepted. Or download software monitored by the National Fraud Prevention Center.

When you receive some overseas phone numbers, or phone calls to promote fraud, be sure to mark them: fraud or advertising to remind others.