Why do Americans (sic) have such long queues? Personally, I keep my hair cut short and don't have a queue at all. Oh - you meant what we call lines? The easy answer is that in some places we do but in most places we don't. Other possible reasons are:

We typically have many more things on a ballot than voting for a single MP position. For example, my ballot here in New Mexico included the President, a Senator, a Representative, a State Senator, a State Representative, County Councilman, Water District representative, about 20 judges, 5 bond issues and 4 amendments to the state constitution.

The polls are staffed with paid employees of the County Clerk's office (which oversees elections here in New Mexico), volunteers and representatives/observers/challengers from the various political parties. However, the numbers of staffers is based upon the anticipated turnout. Heavier than expected numbers result in delays - even when, as now, the number planned for is much higher than normal turnout.

Ditto with polling machines, supplies, etc. My polling place at the primary election planned for 25% more than normal, and still ran out of ballots. We use paper ballots, by the way.

Problems are minimal, but there are always a few. These are typically the result of either misunderstandings or an individual trying to take on authority he or she doesn't have.