Keep in mind that as more people get vaccinated it is only natural that we will see higher numbers of breakthrough infections. Theoretically, if we had a population that was 100% vaccinated, then 100% of the cases would be breakthrough cases, because the vaccine is not 100% effective.
What annoys me is the rule requiring a negative test before re-entry into the US. This is especially galling for vaccinated people. Why? Because the message has been that the vaccines, while not 100% effective, are highly effective at protecting against severe disease, hospitalization, and death. The public health message has shifted -- correctly, I think -- away from "you will be highly protected from disease" to "vaccines are doing their job because you will be highly protected against hospitalization and death." If that is the message, then what is the harm in letting vaccinated people who test positive on vacation return to the States? They might transmit COVID to others, but those people will either be vaccinated or will not. If vaccinated, they will in turn be highly protected against both disease and especially against severe disease and hospitalization. Again, this is the supposed goal of the vaccination campaign. If the returning traveler spreads COVID to a non-vaccinated person, then -- with the notable exception of children under the age of 12 -- so what? I hate to say this, but by this point vaccines have been widely available to anyone who wants one in the US. So if you haven't gotten yours yet, that's your problem.
Yeah, I get that it's a larger public health issue, but it's still annoying that a vaccinated American traveler might face the possibility (however low) of having to incur additional expense and problems if he/she tests positive before their scheduled return home, all because we want to stem the spread of COVID to a population who thus far hasn't done a single thing to protect themselves or their larger communities.