I agree with teapot.

the supply of JYNNEOS available for distribution through the end of this year is estimated to only be sufficient to immunize half of the individuals at highest risk for monkeypox

.

More specifically, ACAM2000 may not be appropriate now for a potentially immunocompromised population.

“Population” just means “group of people with this particularity” in epidemiology, not “the american population.” Nothing in the text you shared suggests america is immunocompromised