>growth since the 40s

The US growth trend has been fairly constant since the late 1800s. There's no real discontinuity in the trend around the time the US become hegemon.

https://upload.wikimedia.org/wikipedia/commons/0/01/GDP_per_...

Part of why Switzerland is so stable is because of its neutrality. Switzerland doesn't have to deal with Russia interfering in its elections the way the US does.