If you want the convenience of just one SIM, take a look at
www.togglemobile.com which can provide local numbers for Switzerland, Norway and Denmark as well as 10 other countries including the USA. It's a low cost PAYG operation.
You will need to activate local numbers. Check the website for more info.
For Turkey, it depends how much you will need a Turkish number. If a lot, get a Turkish SIM. If not much, probably better to use a Toggle or other and roam.