Canada and Australia are smaller but surely count as industrialized western nations (Canada is like 9th by GDP) whose infrastructure was not bombed to rubble.

Here in Australia we just didn't have the population to have a large global influence. We had a population of around 7.5 million in 1945, compared to the US that had about 150,000 million.

The USA's huge population and large internal free trade area give it better economies of scale.

Canada's population was 10mil, maybe less, when ww2 ended.