The British team had to settle for eighth place, with Australia in ninth, while South Africa rounded up the top 10 nations. A total of 20 countries are represented by teams in the FEI World Vaulting Championship.
Although there is a lot of competition left before medals are awarded, the US was happy with their inaugural performance on home soil.
"We went out there, and we just took charge," said Devon Maitozo, team member and coach of the Free Artists Creative Equestrians vaulting club, which constitutes Team USA this year. "I feel like we did one of our best sets that we've done. Just in watching my team, I saw people reaching their potentials in a lot of places and very few mistakes."
The US team's Palatine is a 12-year-old Westphalian who was imported from Germany in 2007 for the express purpose of competing at the Games. He is trained in dressage by team longeur Carolyn Bland.
Leading the female individual compulsory test is Britain's Joanne Eccles, who is competing in the all-female British team along with her sister, Hannah.
The were drawn early, and as they share the same horse, W H Bentley, a French warmblood-Dale pony cross, and their father John is their Lunger, they were on together and were greeted by huge cheers from the British crowd.
Hannah was first and produced a great performance for a score of 7.251 which was good enough for 16th place overall in her first championship as an individual.
There's a great deal of expectation from elder sister Joanne, having won the Female Individual European Championships last year and she didn't disappoint with a fantastic score of 8.157 which wasn't beaten all afternoon to give her the overnight leader's spot.
Eccles said she has had difficulty recently with the initial vault onto the horse's back (called the mount). But the 2009 European Champion pulled it out when she needed to.
"It was my best mount I've done pretty much all year in competition," she said. "That's what actually helped my compulsories, and I think I had a pretty good set. I was really pleased with most of them. There's not much I'd pick out from them that I was really disappointed in," Joanne said.
"I've been practicing the compulsory moves as it's my weakest area and built up to this so I'm really pleased. I know there's pressure on me to do well but I know what I can do, I just have to go out there and do it."
In second place is Germany's Simone Wiegele, with the USA's Megan Benjamin holding third position.
Defending World Champion, Kai Vorberg from Germany, posted a second-place spot in the Male Individual contest when fellow-countryman Gero Meyer on Fürstenlady came out on top. Meyer scored 8,401 against Vorberg's 8,297 while Switzerland's Patric Looser slotted into third.
In individual competition, there remains a freestyle portion of Round 1 before the top 15 vaulters in both male and female divisions move into Round 2, which has a technical and a freestyle program.
"I'm absolutely satisfied, especially with the second part of the compulsories - the scissors, stand and flank," Meyer said. "The first part I had a little more trouble. It was more difficult because my horse was very energetic. He was doing his job very well, but it was a bit hard for me to sit on the horse while I'm doing the mills, for example. I lost balance for a fraction of a second, and I had to correct myself. But all in all I'm very satisfied."
He said that this World Championship is a particularly special one for him. "2010 will be my last (World Championship). I really wanted to be here and I got here, so I'm very happy," he said.
Meyer, who placed second in individual vaulting competition at world championships in 2000, 2002 and 2006, vaulted on Grand Gaudino, a 16-year-old Hanoverian whom Meyer said was "doing his job very well."
Vorberg was also happy with his performance. "I made everything sure and brought it home this round. There were some really good moves which I could do better. You never know what happens, and you never know what you will get, so I'm satisfied. Scissors were quite good, the stand and flank not as good as I can do, but it could be worse!".
The World Games' youngest competitor, none-year-old Robin Krause, competed on the French team, which is currently in fifth place in team standings. And China's first WEG competitor - in any discipline - is Ling Yang, who turned in a score of 6.533 in the female individual compulsory test.
"I can't even put words to how awesome that is," Yang said. "I felt like that was just the icing on the cake for this whole trip."
Countries competing in team vaulting are: Argentina, Australia, Austria, Brazil, France, Great Britain, Germany, South Africa, Switzerland, Slovakia, Sweden and the United States. Countries with individual vaulters are: Australia, Austria, Canada, China, Colombia, Czech Republic, Denmark, Ecuador, France, Great Britain, Germany, Hungary, Italy, Norway, South Africa, the Russian Federation, Switzerland, Slovakia and the United States.
Judges are Suzanne Detol (USA), Jochen Schilffarth (GER), Erich Breiter (AUT), Martine Fournaise (FRA), Monika Eriksson (SWE), and Roland Boehlen (SUI).
The individual freestyle tests for male and females start tomorrow.
Three Vaulting Competitions took place today - the Team Compulsory Test, and the Round 1 Male and Female Individual Compulsory Tests.
20 nations competed in the team competition
33 competitors lined out in the Female Individual Test
14 competitors lined out in the Male Individual Test
Female Individual Compulsory Test: 1, Joanne Eccles GBR 8,157; 2, Simone Wiegele GER 8,037; 3, Megan Benjamin USA 7,856.
Male Individual Compulsory Test: 1, Gero Meyer GER 8,401; 2, Kai Vorberg GER 8,297; 3, Patric Looser SUI 8,253.