Is obtaining a MS degree in Chemistry useful to strengthen your CV if you wish to apply to a top PhD program in Chemistry?
Short answer is yes, you probably should take it or a position like it if you want a PhD from a top US school. It sounds like you don't have many or any papers as a coauthor and your current school's reputation is unknown. So, getting a Masters from a US school with a good reputation, even though it may be a smaller institution could give your application a boost. Also, you will want to see if you can get an internship during the summer with a major research institution while you're doing it. That will open many more doors than the Masters alone.