Bitcoin isn't portable (you can't carry it, try using it without the internet).
All regular currencies are fungible and its super-questionable that BTC is divisible (the network can't handle more then what, a million transactions per second? What's the use of a currency that splits into microscopic sizes if you can't make lots of micropayments with it).
USD may be the most ubiquitous currency on the planet. However, go visit a country like Japan. Once you're out of reach of any currency exchange, you won't have much luck using your USD. Ironically, you'll have better luck using a Visa/Mastercard (which, btw, are not used anywhere other than perhaps ATMs). Those credit cards require a network to be used.
I've been to Internet cafes in Japan. But I never bought a single thing with USD. I don't see Bitcoin having any issues here. Internet is more widely available than places that take whatever your paper currency is.
You can easily take Bitcoin with you. You take your credit card with you. Both require electronic communication to work. There is no difference here.
All regular currencies are fungible and its super-questionable that BTC is divisible (the network can't handle more then what, a million transactions per second? What's the use of a currency that splits into microscopic sizes if you can't make lots of micropayments with it).