Title should read 'confirmed Covid-19 cases by country', that makes a very large difference. Those figures are not to be trusted to begin with so any kind of processing you apply to them does not result in graphs that output a picture that you can then draw conclusions from.
Each country has their own standards in what is a confirmed case and what isn't and some countries actively discourage accurate reporting.
It makes a difference in the absolute numbers, but it doesn't really matter for the trends, since each country's testing policy is relatively consistent with itself. In other words, the graph shapes & trends are stil comparable, whether a country's testing captures 1%, 10% or 100% of its cases.
In some countries it will even matter for the trends. There are some countries that actively cook the numbers to make their politicians look good, and where there are very sudden kinks in the graphs you can be sure that the whole story hasn't been told. As or the testing capacity, that's a big factor too and it is non-linear in many places: testing criteria are changed based on how much stock there is of test materials and how much capacity on the machinery.
The closer to capacity, the stricter the criteria.
The testing policy in most countries is to increase the number of tests over time. How is that consistent? consistent would be testing a random sample of size n every day without changing n.
In addition, some places like the US are really a collection of states. The federal government has little to do with testing policy, so it varies considerably by the state. Producing a total for the aggregate United States really blurs things.
That accounts for the left-right gap between countries as they follow the same trajectory upwards. That is to say, it is almost totally irrelevant when the data is displayed this way.
Each country has their own standards in what is a confirmed case and what isn't and some countries actively discourage accurate reporting.