Please report dangerous drivers to the police - Roadsafe. Report to plod, not just whinge here.

In the case in point, hang>hung is probably the original form, as irregular verbs tend to be older. However there is a tendency for irregular verbs (particularly those ending in 't') to be replaced by regular forms such as hang/hanged, simply because there's a system that you can learn with regular verbs that allows you to construct past tenses easily without having heard the past form already. Hence, dreamt becomes dreamed, learnt becomes learned, lit becomes lighted (in US English, mainly). It's been going on for a long time (Shakespeare switches between variants) and particularly before standard English was developed formally, both forms would likely have co-existed without any issues. Over time, many of these neologisms become accepted and the irregular form is lost. Likewise when new verbs are created, they are invariably regular in nature (text/texted or spam/spammed).

Your example regarding Americans is more to do with sarcasm or irony, and their general lack of facility with this means of expression.

Curtains are hung, people are hanged, it's just the way it is.