The largest democracy takes around two months of campaigning and about six weeks for voting.
Population scales proportionately for both the number of voters and for number of people working on a campaign and number of people working at polling stations on election day.
And let’s be honest, it’s only a small number of states that Presidential campaigns actually focus on because of that whole Electoral College thing.
It’s just the US is accustomed to a long election cycle, that’s all. It’s not a necessity. It may not actually be a good thing as it allows time for bad actors to construct false narratives. Seems to just favour personality over policy.