The findings suggest that cases in people and animals in other states have yet to be identified, the authors say.
The US has recorded 68 human cases of avian flu since 2024.
USDA testing confirmed detections in cats from California, Montana, and Oregon.
Both patients, boys ages 2 and 15 years old, are from Hunan province in southern China.
Among several more outbreaks on commercial farms, one was at a layer facility in Pennsylvania that has nearly 2 million birds.
Detection of the D1.1. genotype, linked to 2 severe infections in people, came from the national milk testing program.
Five new outbreaks are in Missouri, a state that has lost about 4.3 million poultry over the past 30 days.
Also, the virus is confirmed in more US poultry flocks, and European officials share virus details from the UK's recent case.
In related developments, West Virginia officials suspend poultry exhibitions and Massachusetts warns of sick and dead birds across several cities.
Alongside more detections in poultry and dairy cows, the USDA confirmed more avian flu in mammals, including cats and dolphins.
