Africa and other countries

What if every country just retreated back to its borders and decided to mind its own business? What could possibly happen? Every country would be left to figure out its own problems and manage its own prosperity. Yes, there would be plenty of commercial trade but no foreigners would remain in another's country longer than thirty days, even for tourist excursions. What could happen? Weapons would not be allowed to cross borders. Every country would have to manufacture its own weapons if it chose to do so. Defense treaties would be outlawed. Of course, strong, aggressive countries could militarily attack and subjugate other countries but they would themselves be subject to the same actions by other countries. No country would have any legal or moral obligation to step in and defend any other country. What could happen? Would things be worse than they are now?