Say North Korea decides to nuke the United States, but Kim Jong-un is thoughtful enough to do it while I’m vacationing in Australia. Every bit (literally) of digital data I ever had (computer, USB drives, cloud servers) is destroyed. All I have is what’s in my luggage and a piece of paper with my digital wallet’s backup phrase and my public and private keys. Is that all I need to access my funds? If not, what else do I need?
That’s probably all you need, assuming no errors on the piece of paper. The private key is what allows you to perform the transaction, it’s what lets you tell the bitcoin cloud “hey, those bitcoins belonging to this numbered account? I’m the owner, this proves it. Move them to that account”.
Now, your real problem is the value of a bitcoin fluctuates all over the place. A big part of it’s value is demand coming from inside the United States. Without that demand, the value can plummet. Due to the small volume of actual bitcoin transactions, the price is very volatile, which is why they vary in value so much.