Slovakia provided the biggest shock of the Davis Cup qualifiers as they knocked out 2023 semi-finalists Serbia.
A total of 16 nations will contest the Davis Cup group stage across four cities from 10-15 September.
The competition will conclude with the 'Final 8' - quarter-finals, semi-finals and final - in Malaga.
Slovakia dumped out a Serbia side missing 24-time Grand Slam champion Novak Djokovic, winning all four matches on the indoor clay in Kraljevo to reach the group stage of the new format for the first time.
They had lost their previous four qualifiers, but Lukas Klein and Igor Zelenay gave them an unassailable lead with victory in the doubles as Slovakia went on to seal a famous 4-0 win against the 2010 winners.
Brazil also reached the group stages for the first time with a 3-1 victory over Sweden, their third win of this year's tournament after beating China and Denmark in World Group I to reach the qualifiers.
The United States won through with a 4-0 victory over Ukraine in a tie that was played on neutral ground in Vilnius, Lithuania.
Austin Krajicek and Rajeev Ram claimed the decisive point in their doubles match against Illya Beloborodko and Oleksii Krutykh as 32-time winners USA bid for a first Davis Cup title since 2007.
Only two ties went the distance as Germany beat Hungary 3-2 and the Netherlands overcame Switzerland by the same score.
The Dutch side won the final two singles matches to come from 2-1 down against Switzerland. Eight of the 11 sets contested went to tie-break, with Botic van de Zandschulp clinching the decisive rubber 5-7 7-6 (7-5) 6-3 against Marc Andrea Huesler in front of a partisan home crowd.
Germany's world number 24 Jan-Lennard Struff sealed their victory in the final singles match in Hungary, winning 6-3 6-2 against Mate Valkusz, who is ranked outside the world's top 200.
Elsewhere, there were 4-0 wins for France in Chinese Taipei and Czech Republic at home to Israel, while Canada overcame South Korea 3-1 in Montreal.
Finland made the group stages for the second year running with a 3-1 victory at home to Portugal.
And Belgium's Zizou Bergs followed up his shock opening singles victory over Croatia's former world number three Marin Cilic to seal an overall 3-1 victory with a decisive second singles triumph in Varazdin, beating home hope Duje Ajdukovic 6-1 7-5.
In the final two qualifiers still to be concluded, Kazakhstan have fought back to level 2-2 in Argentina and force a deciding rubber, while Chile and Peru are level at 1-1.