Wow you're right. This is conflicting as many of the words are not pronounced properly at all. Maybe it doesn't matter to the accuracy of the speech-to-text system, but it feels like training it with bad data.
If your ML model can't handle multiple accents, it is worthless.
Fortunately, splitting models into separate accent-specialized variants and helping them out with language model training will often help in case the model doesn't cope well enough with the cognitive dissonance.
Which american accent?