Pollen can be carried (as noted by sibling and you) by lots of different insects, and there's myriad solitary and other (by conventional standards) weird bee species around, plus lots of plants are happy to pollinate themselves (tomato is a good example) or rely on wind (corn/maize is the famous example there).
When the common honeybee landed in the continental USA, about four centuries ago, the same people also brought in lots of (other) european plant species that had co-existed with Apis mellifera for millennia.
I'm in Australia, and we only got Varroa in 2022, and it was suppressed for about a year before a regrettable 'oh well' attitude overwhelmed us. The last couple of years has seen a breathtaking impact.
Anecdata - one of my five hives is still struggling on.
Australia's experience since 2022 had (I thought) laid to rest a lot of the 'It's not varroa that's the problem' claims from armchair analysts.
But yes, per my earlier point, lots of our tree crops require honeybees to be shipped in - just because of broadacre / monoculture style farming. Well, along with honey production being its own industry - so they need to follow the nectar, and change up the flavours a bit, but also some trees just don't produce useful amounts of nectar but absolutely require a lot of pollinators for a few weeks only (almonds / peaches I think fit this category).
But yes, there are other pollinators like butterflies, moths, flies, birds, etc.