That’s a major point. When VMC exists a competent US pilot operates like we do in Australia and gets going without delay.
When IMC exists they have very enlightened IFR separation requirements that in practice result in a similar outcome to what competent Aussie pilots do in practice. We can simply bring in rules which allow sensible separation like we have now in G.
Even in Aus not many pilots depart an airport in IMC when another aircraft is in IMC on approach. It’s called “ wanting to stay alive”