We don't have those in America. Mostly because your healthcare is tied to your job, so nobody would risk taking a probationary role that could land them out of work and without healthcare at the end of it...
This is sort-of true. Employment law in the U.S. is by state, and there are only a handful of states that are truly at-will with no exceptions at all (and even in those there are federal exceptions for thew 'protected categories' - race, gender, sexual orientation, religion, national origin, disability that can be reasonably accommodated, etc.). Montana is not employment-at-will at all - you have a probationary period and can only be fired for cause there after that.
America has a thing called the 'Uniform Commercial Code' which is basically templates for business and employment law that states can voluntarily pick and choose from (Louisiana, where the law is based on French legal tradition, uses it the least). But even with the UCC there is actually a lot of variation in state laws on stuff like this.
In my experience outside of Montana having an explicit probationary period is rare in the U.S. You are seeing why in this thread. Your employer may be able to legally fire you at any time, but the social expectation is that they will get the hire right and not fire you for being a mismatch unless they absolutely have to.