As it was said, not all would be using BTC to pay for anything, however, it would spike up the fees greatly, in my opinion.
And affect the chain in many ways, positive at that, I would say.
Even if 5-10% population of those two countries start using Bitcoin for their day to day payments then even that would increase the fees of Bitcoin to very high levels. We have seen high network congestion during the halving time and if number of transactions increase on daily basis then there's chance to see very high level of network congestion unless some layer 2 solution is used.