So you propose that nothing be done then? Toss the 50+ years of pandemic experience from the CDC and WHO out the window because Americans wont listen to their government and have guns???
The whole point is to slow the entry/spread of the virus in the US, which is exactly what the travel restrictions, and quarantining individuals known to have had high risk of contact is doing. Are people going to get through? Yes. Is it going to spread in the US? Yes. Is delaying the the entry and spread in the US, so that the healthcare system can get ready, and so that other seasonal effects, or even new treatments can be found? I'd argue that it is a pretty darn useful idea (as do thousands of experts who thankfully are shaping the response in the US). The whole point of what is going on now, is that we hopefully don't have to start implementing down the road of all the much more severe scenarios you are proposing.
Or I guess we could do nothing.. or heck, have Coronavirus infection parties, and play out survival of the fittest.
@QueenElinor- I was referring to statements from the WHO the other day, that stated 80% have mild "cold-like" symptoms requiring no hospitalization, 14% end up with pneumonia and other complicating factors, and 3-5% end up needing intensive/critical care. I'll see if I can dig up the article/release I was referring to (it very well could have changed in the meantime)
Edit: a quick quote from coverage of a WHO press conference (still trying to find the original transcript) The original version I read was quite a bit more detailed than this: