To your second point it does lose it's "uniqueness" if you begin playing in a tournament outside your region. If Germany suddenly moved to COMNEBOL and was playing Brazil every year or so wouldn't that make a potential Brazil/Germany WC final lose some of it's novelty? Sure, you would still be excited, but the matchup would not be as mysterious as you likely would have played Brazil 2-3 times in the preceding 12 months. Similar to club football and the champions league.
I don't really think it makes a huge difference. A knockout match against a big nation is always special (unless they play like England) and everyone else is just a team you have to beat, it doesn't really matter where they come from. Familiarity creates its own narratives anyway, be it a rivalry, some result/misbehavior that needs to be "avenged" or some streak that needs to be defended. And I'd much rather play the top sides regularly than once or twice every four years.
As for the first point, I think invitations to individual tournaments is fine, just like the US in Copa America a few years ago. It would help with the preparations, especially since the top 3 teams in CONCACAF will not need to qualify for 26. For the long term though I would prefer to stay in CONCACAF and participate in a region that improving yearly. Canada was fantastic and has some real up and coming stars. Likewise, Jamaica, if they can get their shit together, has a great chance to become a solid team.
Well I didn't express it properly but what I thought of in my mind was the USMNT doing this as a 2026 preparation and then evaluating how it went afterwards.
And I think CONCACAF improving to a reasonable level is a bit of a pipe dream, the football world only ever seems to become more polarized.