All settled? Good!

If it doesn't work out I may have a contact for you in San Diego, CA.
This guy has helped several RTW riders before, has space and knowledge.
Let me know and I can forward you some links to find him.
Funny you wait to come to America to solve your "old bike" problems.

Why not rebuild your bikes BEFORE your trip while you are still at home in Germany?
You will be lucky on the AT if it just needs a new valve cover or head gasket. Hopefully nothing more serious.
On the TransAlp, I would have a look at your OIL ... NOW. Is it contaminated with water? If so, it will look light brown or green ... STOP!
Do not ride further until you replace your head Gasket, flush out both engine and cooling system. Get water out of engine case and get OIL out of cooling system, radiator, hoses, water pump.
When water is vanishing ... it usually points to failed Head Gasket and your radiator water is going into Engine.
When water gets into your engine oil ... not good! Could ruin whole engine!
Good luck, be safe!