Wouldn't it make more sense to fight terrorism on our OWN soil???

Counter-terrorism is an excellent idea, but does not work 100% in practice unfortunately, because not all the terrorists can be stopped in time to prevent them wreaking carnage. It does actually depend on whether or not the terrorists actually live in the country that is affected by their acts of violence or they are just visiting to do their rotten deeds. Of course, it the terrorist is "home grown", then yes stop them at home and many countries do have systems in place to stop terrorists but sometimes they get away to another country. Often it is better to stop the terrorist before he reached your country but of course this does not always happen as we will know. Unless all nations of the world unite to stop terrorism, there will still be some nations that will support and hide the terrorists from those who are trying to stop them from their evil acts. All terrorists should be tracked down and bought to justice, irrespective of where they are, because the next time they strike it could be your country. The ones who always suffer when a terrorist does his evil deeds, are the innocent who just happen to be there in the place where the terrorist strikes.