Yes technically the us 'electors' could vote for a different presidential ticket, but that's never happened in practice and even then their options are generally limited by who ran, electors can't pick just anyone.
Virginia’s 23 Democratic electors (Southern) refused to vote for Democratic VP candidate Richard Mentor Johnson due to his open common-law relationship with Julia Chinn, an enslaved woman of mixed race (octoroon). Interracial marriage was illegal under anti-miscegenation laws. They voted for Van Buren (president) but switched VP votes to William Smith (another Democrat), denying Johnson a majority. The Senate elected Johnson anyway.
Nobody ever complains about ambassadors not being democratic though. Same thing goes for, idk, a Secretary of State or whatever, they all go through the same process.
Only when it comes to EU institutions people can't hide their hatred and can't help themselves but make the same old dishonest claim.