West coast of NA - if you're talking the USA portion, don't sweat it too much, your list looks good as is, you will never be more than a couple of days from a bike shop and there are people to help everywhere.

Definitely spare tube for the trailer. I had as many trailer flats as rear-wheel flats. The trailer isn't magic, it just transfers part of the load to its own wheel. I hated hated hated my trailer (older BOB). Nothing but trouble.

For the drive side spoke a kevlar spoke is a lighter way to go than a stein/hypercracker or chain whip.

For the cables, I carry a brake cable, because you HAVE to have brakes, but not a shifter cable, because you can limp along with a broken cable until you find a bike shop. I carry one brake pad and about 6 chain links.

I carry a spare cleat for my shoes, because the ones I use are delicate and hard to find (speedplay). If you use SPD, this shouldn't be an issue.

A few screws for rack mounting, in case those disappear, zip ties, a little duct tape. Maybe a hose clamp.

One thing you can do to really help yourself out is start with a well-maintained bike, and lube and inflate every other day.

Machca, you aren't carrying a freehub now, are you? What a bizarre failure!