No, that's not true. We do know. We absolutely fucking know.
Again, if election fraud was widespread, and people were faking ballots, then when the real voter showed up tp vote, they would be told by the election volunteers that they weren't eligible to vote because their vote had already been cast. This would be occurring hundreds of thousands - if not millions - of times each election cycle.
But it isn't. Out of a sample of 120 million, you'd have a huge and obvious problem.
I think you don't realize the damage you're doing by slandering real elections alongside sham elections. You are protecting the autocrats, and harming democracy, with these baseless accusations.