Including cargo doesn't make much sense to me. Did they include a justification for this?
In contrast, the CDC's take is that "in general, because of poor survivability of these coronaviruses on surfaces, there is likely very low risk of spread from products or packaging that are shipped over a period of days or weeks at ambient temperatures." -- https://www.cdc.gov/coronavirus/2019-ncov/faq.html
What cargo it does and doesn't cover isn't really clear from the announcement. What Trump says often doesn't completely match what the policy turns out to be. When agencies release the actual rules we will know more. I wouldn't be surprised if cargo only meant air cargo.
In contrast, the CDC's take is that "in general, because of poor survivability of these coronaviruses on surfaces, there is likely very low risk of spread from products or packaging that are shipped over a period of days or weeks at ambient temperatures." -- https://www.cdc.gov/coronavirus/2019-ncov/faq.html