Chemistry major eons ago. Especially for upper level chemistry classes I can see why they need to be taken at the home institution. So many two semester sequences (as above for P chem and organic) that one of the semesters abroad likely will leave gaps. I though the concept of a semester abroad was appealing (although finances were a huge problem) but realized the courses available did not work for my chemistry major.
The above post for Germany- it does NOT matter that the country has a great chemistry tradition- like in the US what matters is the specific school you attend. Chemistry is a lab based field and an undergrad with limited experience will not be able to take advantage of the top programs. One needs to decide if taking longer to graduate or doing a lesser course is worth the experience abroad. Life experiences do not end with college graduation. There are grad school/fellowship ones plus just plain traveling. btw- some of those linked courses, aside from not being chemistry focused, refer to attending a “renowned” university.
One makes choices in college. Choosing a STEM major over a social science/humanities major means different course requirements. Within a four year time frame the course and time requirements do not lend themselves to off campus semesters. The time for this would likely have been before getting into the intermediate/advanced classes for the major- when gen ed courses were being done. Of course, as a college freshman a student may not yet realize the desired major will preclude an easy semester abroad.