The two sides had been locked at 13-13 entering the last 10 minutes of the final at the RFUEA Grounds in Nairobi and as extra-time threatened it was two errors by the Junior Eagles which proved decisive.
First replacement scrum half Chris Saint threw a pass into the grateful arms of Marian Drenceanu, the second row then feeding full back Marian Pirvu to touch down.
Patrascu sliced the conversion and the Americans knew a converted try would win the match, but as they pushed for it, the ball went loose and was hacked on for Romania's impressive fly half to beat Tai Enosa to the touchdown.
The fly half, the leading point scorer in the tournament, must have wondered if it was to be Romania's day, having seen a penalty and drop goal attempt to go wide in the minutes before they finally wrapped up the match.
The two sides settled well, neither displaying the nerves they were undoubtedly feeling given the title at stake, with Patrascu kicking Romania into the lead with a seventh minute penalty. He could have given Romania a bigger lead but his next attempts flew just wide.
His counterpart Enosa spliced the uprights with a drop goal before USA took the lead with Robert Johnson's penalty as wing Zach Test began to cause real problems for the Romanians with his pace and running lines.
Centre Niall O'Keeffe, just as Test had started doing, sliced through the Romanian defence to set up the final's first try, which came after Brian Hussey dummied to draw the marker and send Enosa over the line.
USA lost stand-in captain Barry Sheehan to the sin-bin late in the half and it remains to be seen whether this act will prove costly to the Junior Eagles' hopes of keeping the title in the Americas.
Within minutes of the restart it did as centre Ionut Puisoru charged up the middle of the pitch, seemingly delaying the pass too long only for wing Adrian Apostol to retrieve the loose ball and race through to tie up the match at 13-13.
The USA back three of Johnson, Test and Brett Thompson, along with Enosa, looked a constant threat with breaks, but the final pass went astray or they lost the ball on a few occasions to keep the score level at the hour.
POST MATCH REACTION
Romania head coach Mircea Paraschiv: "I am happy. The boys played like a team and I believe we are now a group. We played from our hearts though it was a tough match. It was a good experience for the boys and really want to work hard for next year. From this team now I will remain with only 12 boys who will be eligible to play in next year and it's a good experience for them too. My experience from this tournament will truly be to dedicate Kenyan rugby spirit to the world."
Romania captain Eduard Marinca: "I am happy and overjoyed. I said earlier that our intention was to lift this trophy and true to it God has rewarded our hard work. We knew we had to play and that's what we did, the boys put in a lot of work and gave it all. It's an experience like no other."
USA coach Salty Thompson: "We had control of the game in the first half, in the second half we got the field advantage but unfortunately we didn't score. We put ourselves under a lot of pressure and led to us losing.
"I give respect to all players of both teams, it was a tough match and congratulations to Romania they won. We got tired a bit due to the nature of the tournament. We will now have to focus on next year's qualifiers in Cayman."
USA captain Cameron Dolan: "We didn't come out with the victory, we gave it our best and unfortunately they capitalised on our mistakes. They played well, we couldn't really penetrate their defence and we give credit to them. Respect to the boys, they gave it their best."
RWC 2019 Tickets
RWC 2019 Official Ticketing site NOW LIVE
Fans can now register interest to apply for Rugby World Cup 2019 tickets