Where is Coinbase one available?

As a cryptocurrency enthusiast and finance professional, I'm curious about the availability of Coinbase One. Could you elaborate on where Coinbase One is currently accessible? I'm particularly interested in knowing which countries and regions support this service. Additionally, are there any specific requirements or limitations that users need to be aware of before accessing Coinbase One? It would be greatly appreciated if you could provide a concise yet comprehensive overview of Coinbase One's availability and accessibility.