To be honest missing the occassional 'u' out of a word is the least annoying thing the American language does. Far more irritating is the use of whole different words to say the same thing, or some really bizzare pronunciation, though that may be a more regional thing.
For example:
UK- 'queue' USA- 'wait in line' (that one is by far the most annoying)
UK- 'pavement' USA- 'sidewalk'
UK- 'holiday' USA- 'vacation'
And pronunciation:
UK- herb USA- 'erb
And as for spelling errors:
UK: aluminium USA: aluminum
And I've always spelt it 'doughnut', never seen doughnought or whatever it was before.
There are plenty of other examples, but having lived here for 6 months I don't tend to notice them anymore. Honestly it isn't that big a deal- you get used to it pretty quickly, and I've got used to the strange looks I get if I use a word that isn't used over here.