"You can be fired for any reason at any time."
I see what you are trying to say, but it's not entirely true. You can be fired for any reason, as long as it's not illegal (discriminatory, because of a disability, a pregnancy, whistleblower, union organizer, etc).
This is why often, when you get fired, the company is better off not telling you why (cover their asses). At least that's what counsel of some companies would say.
I've seen the other side of the coin in countries that have employee protections in place. Where it can be abused (ie, everyone is an independent contractor), employees lose as they have no benefits. Where it cannot, employees lose out because it's not worth it to invest in hiring people. Overall, IMO it is bad overall to give employees too much protection. In this aspect, I think the American system is as close to perfect as it gets.