IamSparticles
To get assigned to protect a president? Yes, that’s a pretty tough selection process. The Secret Service has other responsibilities, though. Presidential protection details are just one possible assignment. It just happens to be the most high profile and prestigious assignment. But they were actually chartered as a law-enforcement/intelligence branch of the Department of the Treasury, so they also investigate a range of financial crimes, including (but not limited to) forgery, counterfeiting, wire fraud, etc. At the time that it was decided the president needed constant protection (after McKinley was assassinated in 1901), the FBI didn’t exist yet, or else they might have gotten the job.
There are plenty of states where you can vote without having to show identification at the time of voting. You do have to register prior to voting, though, and that process requires identification and proof of residency. And no, none of this has ever resulted in any significant voting fraud. Between 2000 and 2014 there were only 31 documented cases of voter impersonation in the entire country.
If they don’t jump through whatever hoops they are supposed to to prove they are citizens, then yes, they will be removed from the voter registry. I don’t know if you’ve ever had to prove you are a legal citizen before, but it isn’t super easy. It takes time and money to get the proper documents.