Netflix 4k streams are like 25Mbps at best. The US average broadband speed in 2017 was around 50Mbps. There is no problem getting 4k to consumers.
Whether or not they have a 4k display... that is probably the blocker. I have a 4k display but it's not my primary display (instead opting for a 165Hz 1440p panel) and I never bothered to buy a 4k TV, given how dirt-cheap high-end 1080p TVs are. Would much rather have the black blacks of a $500 1080p OLED TV than a $3000 washed-out 4k LCD.
That average broadband speed is deceptive, because it includes people who have gigabit at home. The more interesting number is the median speed. But even using averages, not a lot of countries yet have the speed to support 4K streaming[0], and like you said, even if they have the bandwidth, they need the equipment.
