when you say "travelers from china", it is parsed by the viewer/reader as "chinese people". this like thin veneer of "well technically it could be white people who were in china at the time" isn't enough. part of the ad's central message is "trump tried to keep all the chinese people out, but he did it so ineffectually that some still got in - how dare he, scary music, ominous graphics". regardless of the technicality of the wording, that is the message the ad conveys to the average viewer.
also, I honestly don't get why this is the strategy here. why is biden trying to fight trump over who china likes more? all it does is deflect from how terrible trump's response to this has been, by casting a different country as the actual villain. by suggesting that the problem is that trump didn't do great, but part of what he didn't do great was that he listened to the real bad guys. why not just... not do that? if he brings up china, just call him out and say he's intentionally trying to shift blame away from himself. point out that the american government knew about this shit in december (and knew it had spread to other countries by mid-january) and did nothing. he did nothing. blaming china is just a distraction.
every minute spent saying "trump got played by china", rightly or wrongly, is a minute that you're not saying "trump literally had people telling him about this shit months in advance and didn't bother doing anything, because he cares more about his stock portfolio than your life".