Really, do you remember the outrage there was when trump restricted flights from China?
Imagine what would have happened had he done that from Europe in January or February before it was too late?
1) How does that mean that the US system wasn't built to handle this crisis?
2) So what? What ultimately came from all that noise? The ban stood. To be President of the greatest country on Earth, you need some beitzim. If noise stops you from keeping the country safe, find another job.
3) If the ban on international travel had been done all together, the reason for the noise (racism) would have been moot. That's not to say that the politicians wouldn't have found another reason (maybe nationalism). But just like the noise about the flights from China, they would have subsided when the rest of the world's infections were spiking in March and April and ours would have been much, much lower.
4) If the President was more politically savvy, he would have quietly invited Congress to make the ban with him, in a show of solidarity for US safety. If they would have turned him down and made noise about it, they would be risking handing him the election on a platter if he turned out to be right. More likely they would have grumbled about nationalism and why we aren't doing more to help the countries who are getting hit hard.
5) Your arguments speak to the political mess we currently find ourselves in, not the way our system is actually built. The fault is in the people of our government, not the powers constitutionally afforded to them.