If you are living in those developed countries, it is not very hard to find a place or a person who willing to convert your fiat to Bitcoin. However, if you live in some under-developed countries, I doubt that this activity will be easy. As you can see, some third world countries dislike Bitcoin. Moreover, the people in these countries dont even know what they will do with Bitcoin

I'm using exchangers site many times in our country and It's safety because their sites have a good feedback. The best way is to find an legit exchangers and convert your bitcoin to cash. Why do you need to convert your bitcoin in other country? It is safety if many people tried to used this exchangers before.

I live in 3rd country and it's super easy to convert my bitcoin to cash using local exchanger, all you have to do just send your bitcoin to the exchanger and sell them after that, you will receive your money on your local bank account, in my experience bitcoin is friendly here south east asia specifically, you might right that converting bitcoin to cash in 3rd country may be hard but maybe in some countries in africa. So far we have never faced any problems in converting our bitcoin to fiat.
Anyway the best way to convert your bitcoin to fiat are using local exchanger or localbitcoin.

I thought for a few large countries already have several ATM machines to get cash from selling bitcoin quickly only country I have not been too many ATM machines bitcoin, at least faster in my opinion to sell bitcoin with cash or other means to find a site exchange fast transaction support in my country

You may have heard of Coin Base, a bitcoin buy/sell place and wallet. That's convenient since it partnered with PayPal, it made things easier for me when I want to exchange my bitcoins into PayPal balance for purchasing computer parts online. I can cash-out my PayPal balance by withdrawing them to my bank account and then just wait 7 business days and go to the nearest ATM.

For me the fastest and most convenient method of cashing out bitcoin is lead through the exchanger Bank account. In addition, a lot of people of my friends makes a purchase on the Internet. I pay them bitcoin, and they give me cash.

If you want fastest way then, trade with friends or very close known people. Because the exchangers will wait for BTC to process, after they will provide cash. Coinbase is nice I heard, but not supported in my country yet.

There are several ways to convert you bitcoin into in real money, there are some exchange who accepted credit card/debit card which is connected into bitcoin. its been delay sometimes in the confirmation in the blockchain. But here in my place we can transfer bitcoin directly to to the buyer which you can also do the same thing actually.

Well first you must find a bank that accepts bitcoin for a exchange money i really tried it finding some of the banks here just to cash out my bitcoins so i exchange wallets because the wallet that i used they don't have access to the bank here in my country so that i change wallet in order to exchange money to the bank here or trade it to someone you know that really needs bitcoin or sell bitcoin in to real cash its easy bitcoin now a days is very popular you can double the payment if you sell bitcoin