... Ultimately, yes, we achieved our manifest destiny of one nation from sea to shining sea.
"Ultimately" never occurs. I.e. it is still somewhere in the future. Thus US's "manifest destiny" is subject to change and best understood for practical purposes as what is likely to be the conditions several generations from now.
What do you think those conditions in the will be?
I will give my expectations for period when recovery from the Great Depression, GD, is complete:
Living standards will be approximately what they are today, but people will once again seldom, if ever, travel more than 100 miles from where they were born. Traveling farther is a waste of time, expensive, inconvenient, generally useless when they can VT (virtual travel) the world instead via the fiber optical trunk lines and the local terminal RF links. Most will live on the "entitlement" and many will practice a skilled craft (everything from painting, silver smith, wood carving, etc. hobbies with products often given as gifts or sold on eBay etc.) and many will be into some spiritual cult for meaning in their lives.*
The US's main economic trade activity will be food, fiber and coal production for Asia (including India / Vietnam region). The "Waynelands" region of US will be the bread basket of the Asia, as wheat becomes the equal of rice in Asia's diets. This production is highly automated, very few farmers or miners. The directly employed are mainly machinery repairpersons (Called "repairers." Calling them "repairmen" in public, which of course includes your forum post, blogs, and Emails, can get you finned.) Hong Kong, Dubai and Mumbai are the competing financial centers, with branches in less important cities such as NYC and London. Paper money no longer exist - only the global IC€, which is pronounced "ice." (From Internet Conversion Euros, but like "Laser" few remember the origin of this name. Most falsely think name comes from "international currency exchange.")
SUMMARY: US's "manifest destiny", after the GD recovery, is to be a contented colony of Asia trading food, fiber and coal for industrial and agricultural robots that harvest the wealth of the "Wayneland" region.
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*Including even the popular Salem Witch Guild and its local covens stretching from sea to shining sea. (Silver haired Sandy {quite old then} probably will be a high priest in one as disillusioned, like many others, with God who failed them in the GD.) Note "priest" is a "unisex" word also as "verbal discrimination" is illegal.