Non-vaccinated Americans should not assume they are safe from Covid-19 simply because many of the other Americans they encounter are vaccinated. The problem is that the fraction that are vaccinated is insufficient to reach herd immunity; the virus still circulates and you can still catch it. And in some regions, it is even less.

Indeed, vaccinated individuals can catch the disease and spread it, and may not experience any symptoms. This is less likely for vaccinated individuals than for non-vaccinated, but the chance is not zero.