I would argue that gotten makes far more sense than using got for the past participle (cf., forget, forgot, forgotten). It was likely sloppy or poor grammar that ultimately lead to got overtaking gotten to become the more common form in the UK, so got as the preferred past participle in this country isn't something of which I'd be particularly proud.
With regard to allot/alot, I can't really see how the Americans could be blamed for this. I've lived in the USA, Australia, and the UK and the problem is endemic in all of these countries, unfortunately. That said, I too find it particularly annoying and have also noticed a similar development with abit.