This is the first time (in 45 years) that I've heard of acting on a mid-term teaching review. Even a mid-term review is, I think, very rare. At least in the US. Students here usually provide a course evaluation at end of term and the department head is open to student complaints at any time, but I think that any formal system of supporting struggling teachers is also very rare. Prior to obtaining tenure, you are subject to being fired for poor teaching at many places. But, in general, it needs to be a pretty clear cut case for that to happen.
Instead, poor teaching is dealt with at the time of hiring and often as part of the tenure process, including at mid-tenure review. At most places, poor teaching is a mark against you, though at some universities a star researcher will still be hired. Such a person won't normally be put in a class room with novices, however, and teaching will be at upper levels where advanced students may be more able to deal with it.
Generally, though, if a major part of the job is teaching, you are expected to already be good at it in order to be hired. In many of the top research institutions where teaching isn't really expected of researchers, there is a special faculty track for teachers who handle much of the undergraduate program. These jobs can come with (eventual) tenure and a different set of responsibilities from those on the research track.
In many fields people are employed as TAs as part of the doctoral education and some of these positions involve actually teaching a course. Thus, you can get some experience teaching before entering the job market. That isn't universal, of course. If a TA turns out to be a poor teacher, they won't be put back in a classroom (one hopes, at least) and will be given other duties.
There are also, in some fields, special interest groups who hold conferences dedicated to teaching that subject: SIGCSE as part of ACM, for example, which holds several conferences per year. Here teachers can learn about the craft of teaching. But it is up to the individual, with encouragement from the administration, to participate in such things.