It did, however, dramatically help the U.S. We got the atom bomb, moon landings, computer, and many other inventions out of European immigrants who fled the Nazis. The U.S. had a strong science program before the war, but its superpower status afterwards was just as much because we got all the brightest minds in Europe as because we bombed everyone else into rubble.
I could see Australia, New Zealand, or Canada similarly benefitting if the U.S. turns towards xenophobia & warmongering.
Some of the major postwar US innovations — particularly in the space program — came not from European immigrants who fled the Nazis but rather from German immigrants who were the Nazis. US intelligence services brought them here through Operation Paperclip. https://en.wikipedia.org/wiki/Operation_Paperclip
One big problem is economies of scale. The U.S. has more than five times the combined population of these three countries. A similar problem affects the Nordic wundercountries. They are some of the richest and happiest countries in the world and have some of the best education systems in the world, but their small population sizes hinder their sheer economic potential. Finland's population is only 5.4 million and Sweden's is only 9.5 million, and yet they still gave birth to Colossal Order, Spotify, Supercell, Rovio among others. Imagine how many tech powerhouses would come out of the Nordic countries if they had larger populations and thus larger economies of scale. Same with Norway. For years its economy has been tied to O&G, but with the collapsing price in oil the Norwegian government is investing their oil billions into startups; in the coming years, Norway's startup scene will explode. And all with a population of 5 million. If their population was larger, I think Norway's startup scene could be so, so much bigger.
One possible issue with the Nordics usurping the US's lead is their Janteloven which can work against entrepreneurship. However, other European countries may be able to take advantage, the UK, DE, FR (to a lesser extent due to regulations).
It's interesting you bring up warmongering when it looks like some in the opposition party are concerned about the US receding from interventionism and seeking more effort from the other NATO countries. That the US is becoming more isolationist --which would seem to contradict the US becoming more interventionist.
Modernization? Do you think it's likely he'll be more interventionist than the Obama years? It's hard to imagine that, but of course it's possible, the question is is it likely?
Obama was actually very restrained in foreign policy - far moreso than Hillary Clinton would've been, for example, and also moreso than Bush Jr., Reagan, or even Bill Clinton. He's relied largely on drone strikes and covert assistance, while the other presidents mentioned actually invaded other countries. Obama's own national security staff criticized him heavily for this.
Anyway, I didn't mention political parties in my original post, and AFAIC trying to make this partisan is just projection. There are hawks on both sides of the aisle: the Democrats are milking Russophobia for all it's worth and seem to want to start a new Cold War, the Trumpists see the world as a clash of civilizations between the Judeochristian West and Islam, and old-line Republicans like McCain and Graham are very skeptical of Iran and China.
I don't mean to take it into the ideological realm. I can't disagree with what you said, except the money spent on foreign wars/intervention was pretty ramped up during Bush II and Obama.
I could see Australia, New Zealand, or Canada similarly benefitting if the U.S. turns towards xenophobia & warmongering.