It's only a one-day strike. Unless you're openly an organizer, you're not taking much risk. The biggest thing you're thinking about in that situation is going without pay. But also, this is why strikes are only successful when you've got everyone taking part in them. The cost to replace an entire workforce is actually huge, and would shut down operations for a period of time. There would also be a campaign aimed at preventing folks from crossing their picket line: customers, new staff, etc. Enlisting elected leaders, etc.

More generally-speaking, it's illegal to fire NLRA-covered workers for striking. Granted, the penalties are minimal (penalties are backpay MINUS what the worker earned while they waited for the case to resolve itself... no punitive damages). Also, you have to actually win in court, of course -- and I'm guessing Amazon has good attorneys that can win a tough case. But if you're firing the entire workforce, no attorney is that good. It's clearly retaliation.

It's true that during economic downturns it can be hard to successfully organize, people in all industries feel more replaceable. But it's also true that at times when workers are feeling more pain, there can be tremendous activism. Additionally, there have been times in our country's past when workers were far worse off than today and yet risked far more than their jobs (in some cases, their lives) to win the protections we have now.