If you're riding in from Mexico, you will have NO PROBLEM entering the USA regards your bike.
What you CANNOT DO is permanently import the bike into a USA state.
(not easily anyway) But as a tourist, no problem and no paperwork need be done. You just ride through!
But at the border it's YOU they will be concerned with, NOT your bike. We don't do TVIP's and any such nonsense found in the 3rd world. No carnets, no imports papers. They won't even mention your bike. It's not Homeland Security's job. They WILL run your plate to check to see it's not reported as stolen.
Local police deal with vehicles. If you get pulled you will be OK as long as you have some sort of Title or current registration to show The Man. You keep whatever plate is on your bike, but you should have registration or title that matches and a valid driving license.
You can sell the bike (illegal) but buyer will NOT be able to register it as it's of
Chilean origin. It shows up on our DMV computers as red flag. No GO.
I've crossed into Mexico with my Danish friends riding German registered BMW's. No problem, they only looked at their passports to check their Visas.
USA don't care about vehicles. That is the States responsibility and local police.
Most cops will only run your plate to check to see if it comes up reported stolen, if not, your'e free to go.
They also are not empowered to to check your Passport or Visa. Use your home country drivers license, should be all you need. But of course you WILL need a Visa to enter USA ... or maybe certain "most favored nation" folks can just drive in? Not sure on that.
US citizens can just drive into Canada (and vice versa) without visa. Certain countries' citizens can also enter USA without visa ... not sure Which.