When a timing belt fails…the engine stops running. Interference engines…there’s a chance that a valve could hit a piston before the valves stop moving. I had a belt break once on a interference engine…but no engine damage. It’s rare, but it does happen.
What do you mean by “Causing” catastrophic failure. Timing belt can…but a if a transmission fails…it’s not “Causing” the catastrophic failure…it “IS” the catastrophic failure.
Just keep up on maintenance. Automatic transmissions need maintenance (i.e. fluid change). Engine oil.
Your owners manual is a good source for what services and when they are needed. Just follow the maintenance schedule in your owners manual and you’ll be fine.
You do NOT have to take it to the dealer for ANY service. Either do it yourself (like many of us here do)…or find a good local mechanic (which I recommend for those who don’t do their own PM).