The Delta variant, first seen in India, is more contagious and causes worse illness than the original.
Chickenpox has an R0 of 10-12. The original Covid was about 2 but the delta variant is about 6 to 9. So it speads faster than the original Covid. The amount of virus that you need to breathe in to get infected, is lower.
If you're unvaccinated, you are 8 times more likely to get Covid than if you're vaccinated.That's nice, but a mild case of coughing and sneezing isn't a worry. What is bad news, is if you get so ill that you go to hospital. And vaccination reduces that chance 25-fold.
The chart below shows you how evolution has made Covid more infectious. It is now as infectious as chickenpox. It's a bit more deadly than seasonal flu, but it's a LOT more infectious.
Vaccine refusal is going to hit the USA hard, and I don't see any way to avoid that. In the USA, the pandemic has been highly politicised. But we aren't immune to vaccine refusal here.