Should I stay an extra semester to complete a second minor?
Basically, a second minor doesn't really convey any additional benefits to you in terms of admission. It just means you've done enough courses in a specific area to be recognized by your specific school as having completed a "minor." Some schools in the US (and most foreign schools) do not offer minors, so it won't make a big difference.

Also to consider—if you are planning to do graduate school after your bachelor's degree, taking an extra semester in the US likely means that you will have to wait a full year before starting graduate school. This can have significant impacts, as you will then need to find something to do in what would have been your spring semester. There is also the possibility that, because you will be out of school for a while, you may need to start repayment on any student loans you have. (Usually you're allowed a six-month grace period before repayment starts.)