[alchemism]

Fun fact: a successful invasion of the North American continent has very little to do with weaponry and more to do with logistics and projection of force across an ocean. There is only one superpower with the capabilities to do it at all.

[inglor_cz]

If you are OK with US isolationism, then your fun fact is very salient.

If you'd like to keep the US-led coalition of mostly free countries intact, then your concept of the US military needs must include a lot more activity that just "defending from a hypothetical invasion of North America by Old World powers". Defense of allies elsewhere, keeping trade routes on the ocean open and safe.

I think the fiascos around tariffs demonstrated quite nicely why glorious autarky is no longer an option. Too much stuff is produced elsewhere, from resources to highly specialized products like icebreakers.

[SubiculumCode]

Yes. Right now...because the U.S. had the biggest baddest military that the world had ever known. If we had not had that, someone else would have made one. It's one thing to forgo an option that does not seem viable versus expecting the same decision when it is.

[alchemism]

You mean like the British Empire? ....The Spanish Empire maybe?

The only modern contender, the Japanese Empire, arose partly by the encouragement of Teddy Roosevelt.