from the numbers I have seen, home births in the USA are on average even more dangerous. Which is really saying something since the hospital system is so bad.
The numbers I first saw on this question years ago were from Britain, which showed homebirth safer than hospital birth. Previous times this discussion has come up the medical advocates are always explaining away the reletive safety saying high risk patients default to hospital; this is the first time I've heard homebirth being less safe. So I'm not sure what's up in the US. Well I have some theories...
First, a lot of people in the US live quite a ways from the hospital (something that has grown worse with time). Whatever their problems, hospitals have a lot of personnel and equipment for worst case scenarios that a home doesn't.
Secondly, a lot of people doing homebirths do it to avoid the hospital. And hospitals have responded to competition from midwives by refusing to work with them and keep them out, by working to outlaw midwifery, and the like. So a lot of parents are motivated to avoid the hospital; meaning some won't transfer when they should or won't transfer soon enough. Or they'll transfer to a more distant hospital to get one that is friendly to midwives or natural approaches.
Third, people here are very unhealthy on average. That means more complications than other countries; which in a non-hospital situation are more likely to not be handled. Midwives also tend to be dis-proportionally used by certain subcultures which have higher incidence of disease due to genetics and/or lifestyle. When you compare the US to Canada, you have to keep in mind it's not just our birth outcomes that are several times worse; we spend several times more on medical care in general. The US spends more per capita on medical care than any other country in the world.
Then there is the question if we should really trust data from US sources on the issue of midwives. Medical science here is only about 40% replicatable (worse than coinflip) and they have a proven anti-midwife history.
Homebirth has really exploded the last couple decades. I wonder if the difference could be tied to the relative inexperience of recent entry midwives?