I would argue we do an excellent job investigating election fraud. We have a system with a fail rate in the millionths of a percent. And of those, the vast majority are failures to update addresses or clerical errors.
Can you name the last time that a U.S. federal attorney performed an in-depth investigation of election fraud? The only instances of this in 5 decades are the recent investigations in North Carolina and Texas.
There are no examples beyond this of large scale investigation of election fraud in the U.S. -- you can hardly call something that is never done "excellent". You don't know the failure rate in the U.S. because it never has been investigated. The only time people are picked up for election fraud in the U.S. is because they bragged about it (generally on social media). This how the recent 19 convictions in North Carolina came about for the most part. It's not like the DA had to actually do much investigation to indict in these cases.