Maybe consider dividing your journey up into parts. Geographic parts.
New travelers waste a lot of money shipping their "prized" baby across the world. Get over it. Your bike is important ... but really just a tool. Expendable.
Budget an issue? Learn from the Pro's.
South America and back on a 250 Super Sherpa Minimalist Adventure - ADVrider
John Downs is a HUBB member but posted his fabulous Ride Report on ADV Rider ... as he has plans for a book. This guy knows how to travel on the cheap.
Or ...
Look at what Dr. Greg Frasier does. He has several bikes stored around the world. Or he sometimes buys and sells a bike for a specific trip. Even rentals sometimes make sense. (like Thailand, Cambodia or Vietnam)
The fact is ... Shipping or Air freighting a bike from continent to continent is a major PITA. The smart/broke (read: experienced) riders don't do it often. You can travel on nearly any bike ...if you know how.
Never get attached to a bike. They can be here today, gone tomorrow.
If you want to take your $25,000 BMW GS to every continent ... have at it. But you will pay: In Time, In Money and in ...STRESS!
Since you're in the USA, why not start there? (unless you've seen too much of it ... like I have) In that case you could go to Canada ... and fall asleep from boredom and pick up a few speeding tickets. (since they have no crime ... they go after tourists on bikes!

You could do Alaska ... if you like One Percenters and drunken X Pat Hill Billy's and Indians with too many guns.
AK is beautiful but the local clientele aren't my favorite folks.
The real trip will start in Mexico. The most under rated country in the Americas. Few HUBBer's have really ever seen it, lived it or know it.
Most RACE through it ... on a mission to Panama ... a royal shit hole, IMO.
Mexico is quite diverse ... a diversity most motoqueros never know.
So start in Mexico (good for two/three months easy) then continue South.
No Carnets or Visas required for any countries, far as I know. But some countries now charge substantial fees for a Visa ... like Bolivia ($130 or so?)
(about four months pay for an average Bolivian)
By the time you reach Ushuaia, Argentina you'll have to decide what to do:
1. Ship bike home - $$$$
2. Sell bike to someone local ++$$$
3. Ship bike to Africa, Australia or where ever! - $$$$$
About 80% of new HUBB members come a go quickly. They never end up going anywhere. Most put up less than 20 posts and are gone ...