There were few test kits available. Of those some had flaws.
There were only 5 test labs who could process them
There will be 40 labs soon
So the apprearance of no problem in the US is deceiving. We don't have the information we need to make that assessment. As testing occurs more cases will be discovered. Meanwhile the infection is spreading.
Why is the US caught so flatfooted?
Dumb don gutted programs and departments that were set up to deal with pandemics