@mediocre
First off, I am an idiot on the internet. So, with that said use what I say as inspiration for you doing your own research. Never trust an idiot on the internet and never trust a single source of data when you research. I am going to be brief below and overly simplify some things. Now onto me yacking like I know something.
The US was very slow to respond to the outbreak. It was highly foolish, but considering our leadership, expected. I cannot stress enough the importance of gathering initial data for a new virus, bacteria, disease or whatever. In this case it was needed in controlling the spread of SARS-CoV-2 along with learning more about how easily it spreads and where it has already spread. It took a long time for it to be taken seriously and a long time for testing to slowly ramp up.
The total number done is not the correct way to look at it. The more important factor is how many you do daily. You have to get an idea of factors like the percentage of the population who is asymptomatic. We also need to get an idea if we are about to get a surge, like if there are mutations or if opening a state up is about to cause a catastrophe and we need to shut things down again. You have to act fast or risk exponential growth. Part of this was to lessen the influx of patients into the hospital. We also have to test a large number of people, not just the ones we think are sick. You want the tested number of infected to be less than 5% of the total tests done. If it is higher than that then your testing isn't not broad enough and you are focusing too much on the obviously sick which doesn't do anyone any good. The 5% rule would take a bit to explain and I am lazy.
Lastly, keep in mind the tests are not very accurate, currently. I believe they are hovering around 70 percent. There are high rates of false positives and negatives, so multiple tests per person are needed. You want to test before they are sick, during them being sick and then follow-up because you want to know if we are building an immunity to this or if people are getting re-infected. When the tests aren't accurate you run into issues of telling people they are sick when they aren't and telling them they aren't when they are.
Let us say you come in sick and test positive for COVID-19. I then run the test again and get a positive result. I send you home and after a week you come back and I test you again, it shows negative. I test again a day later, it shows negative. Fine, it looks like you are cured. You come back for another follow up and you are positive. Well, did you get infected again or were the two previous tests false negatives? This is the headache we are running into and why more tests are needed. The accuracy blows sandy camel dick. If normal camel dick wasn't bad enough this camel just fucked a sand dune and now its a sandy camel dick.
Hopefully, that gives you a decent idea about the importance of testing and why more tests are needed.