Rory , are you an American citizen or resident returning home on the Chilean plated bike ? In that case you can ride the bike into the USA provided you get it covered for US-liability insurance for a permitted period . You or anybody who buys it from you will not be able to get it re-plated as a road bike in the USA . But you can keep it as a paperweight or souvenir in your garage and play around on private property . You can sell it to another person with the proviso that it must never be used on public roads .

Or are you a tourist going into the USA temporarily ?
Then as a passing tourist you will be permitted to ride the bike around the USA for perhaps six months , the length of your tourist permit and then it has to be removed from the country. Foreigners are (or were) permitted as a reciprocal courtesy to ride any motorcycle they bring from their home country to travel the USA for a limited time as Americans are permitted to do in the countries they visit.

Or are you an immigrant taking up residence in the USA for a prolonged time ? Then at the border US customs may get a bit finicky about the bike .
. But you will not be able to get it registered and plated in the USA unless it is an old antique , beyond a certain age .

With all the international concern for pollution control and safety there is a budding trend among the major brands producing touring bikes to eventually make all motorcycles compliant to the strictest regulations ( sales !) Maybe the bike you are considering is one of those ?

The US does not engage in issuing temporary import permits at the border . The border patrol people at the portals do not seem to care much about those things unless they suspect blatant smuggling or other crime . The problems of ownership, registration or taxation will become evident later if one has contact with police ( traffic offenses) or tries selling and changing over ownership documents .

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http://advrider.com/index.php?thread....207964/page-5 then scroll down to post #93