Siniakova, the world number 31, then saw off 63rd-ranked Riske 6-3, 7-6 (7/2). Serving for the win at 5-4, Strycova sealed the deal with a backhand volley victor to deliver the first point for the Czech Republic.
The U.S. team, though, had to rely on three Fed Cup newcomers as they were missing Serena and Venus Williams, holders of a combined 30 grand slam singles titles, along with world number six Sloane Stephens and Madison Keys, semi-finalist at both Roland Garros and Flushing Meadows.
Barbora Strycova of the Czech Republic will take on Sofia Kenin in the opening match, followed by Katerina Siniakova against American Alison Riske in the second rubber of the opening day on Saturday, according to the draw made on Friday.
"In the second set I got a lot of break opportunities but she just played too good so credit to her".
It was the ideal start for the Czechs, winners of five of the last seven Fed Cup titles, who are without two of their top players. "I couldn't be more proud", said United States captain Kathy Rinaldi, fighting tears at a press conference.
Strycova, playing in the last Fed Cup tie, went a set down in Prague to Kenin but won 6-7 (5-7) 6-1 6-4.
Sofia Kenin is scheduled to play Barbora Strycova in the opening singles on Saturday on an indoor hardcourt at the O2 Arena.
But the 32-year-old Strycova called on all her experience, bringing the home crowd back into the match by racing ahead 3-0 in the second set and securing the set four games later with a big serve that Kenin returned high and long.
Strycova, who was tearful during the national anthems, said: "It's amusing because it's her first tie and my last one".
"I think I definitely do like the court a lot and any time that I'm indoors".
Rinaldi helped the US a year ago win an 18th Fed Cup, but first since 2000. But the American put up a fight and narrowly missed forcing a tiebreak before Siniakova took the first set with a strong forehand smash.
USA captain Kathy Rinaldi said on wtatennis.com: "We came here expecting their best players to play, so we were preparing for everyone".