The Americans, whose only previous experience of ODI cricket was at the 2004 Champions Trophy, thrashed Hong Kong by 84 runs to wrap up a top-four place in the six-team competition.
There will be 20 ODI nations after the end of the tournament, with the top four sides to join Scotland, the United Arab Emirates, Nepal and the Netherlands in having temporary status.
The United States will now be able to play 36 ODIs in the next two and a half years.
“Moving forward, playing competitive ODI cricket for the next two and a half years is another level, bringing the team to this will require more hard work,” said USA coach Pubudu Dassanayake.
After an opening loss to Oman, the US beat Namibia and Papua New Guinea to leave themselves one win away from their target.
Former West Indies batsman Xavier Marshall hit 100 as the Americans made 280-8 batting first on Wednesday, with Hong Kong managing just 196-7 in their run chase.
“As a team, we have worked really hard for the last two and a half years and we have targeted this tournament,” added former Sri Lanka and Canada wicketkeeper Dassanayake.
“The boys are feeling great. It is a big achievement as the USA has never been to this level before.”
Oman have also secured their ODI status, leaving Namibia, Papua New Guinea, Canada and Hong Kong to fight it out for the remaining two places.