Most votes in the USA are counted nearly immediately. By the end of the evening, we have a pretty clear picture of the in-person votes.
The issue is the mail-in votes. Some states end their mail-on votes a week or so before Election Day, so they are all in. Other states, like California, allow mail-ins to be posted on Election Day, which means they might not arrive to be counted for a week, holding up the process.
I'm not big on most of these "reforms" to the voting process that MAGA wants, I understand what their true agenda is, but it makes sense to demand that the mail-in votes arrive by Election Day. That's a sensible change that would help the entire situation, and keep MAGA loudmouths quiet. It's not a good system when we're still waiting on a result a week after the election, especially when we're mostly waiting on a giant state like California, while we have to listen to MAGAs torture the world with their incessant whining.