Results from American elections often arrive over several days while other countries report overnight. The difference lies in how the vote is administered rather than in efficiency.
There is no national election authority
Elections are run by states, and in practice by counties and townships within them, each with its own equipment, staffing and procedures.
A single national contest is therefore thousands of separate administrations reporting on their own schedules under different legal rules.
Because the rules differ, the same ballot cast in two states can be processed at very different speeds, and neither is doing anything unusual.
Mail ballots carry extra verification steps
A ballot returned by post arrives inside an envelope that must be checked before the ballot can be separated and counted.
Verification may involve matching a signature, confirming a witness, or checking identifying numbers, and each of those is a manual step performed on individual envelopes.
Only after verification can the envelope be opened, the ballot flattened and fed through a scanner, and the sequence cannot be compressed without weakening the check.
Some states forbid early processing
Several states prohibit election officials from beginning any part of this work until polls open or close on election day, even for ballots received weeks earlier.
The stated reason is preventing partial results from leaking. The effect is that a large pile of envelopes is created before any of it can be touched.
States that allow processing in advance report far faster on the night, with the same ballots and the same checks.
Deadlines and cure periods extend the window
Where a ballot postmarked by election day may arrive afterwards, the count is not complete until that window closes.
Voters whose ballots have a correctable defect are often given a period to fix it, which is a due process protection that necessarily delays finality.
Ballots from military and overseas voters have their own extended deadlines for the same reason.
Projections are not results
News organisations project winners using statistical models on partial returns, which is why an outcome is often known long before certification.
Certification is the legal act, and it follows canvassing, reconciliation of totals and any recounts triggered automatically by a narrow margin.
The gap between the projection and the certificate is where most public confusion sits, because the two are frequently described in the same language.