I don't exactly understand why all this stresses you as much. Maybe because you are new to banking and insurance ? Personally I saw a lot (although as far as American express is concerned my experience has been good so far), and I just follow common sense policy often advised in this forum : never rely on one card. It can be gone tomorrow.
So if tomorrow American Express does not want to make business with me no problem. Same for another card. On the other hand if one day I find Amex card useless (as some of my friends, but they don't travel often) I will say bye.
The real problem is when you have a company and you rely on credit from a bank or financial institution. They can kill your business. But for personal card as long as you have a few of them, nothing wrong will happen to you. At worst you'll go back to cash and prepaid cards, which is not incredibly bad.