What countries is Coinbase not available in?

Could you please inform me of the countries where Coinbase is not available? I'm considering expanding my cryptocurrency investments, and it's crucial for me to understand the geographical restrictions of various platforms. I've heard that Coinbase has a significant global reach, but I'm also aware that there may be certain regions where it's not accessible. Could you please provide a list of these restricted countries or regions? It would be greatly appreciated if you could also provide any insights on the reasons behind these restrictions. Thank you for your time and assistance.