World number seven Tomas Berdych crushed Andy Roddick in just 61 minutes at the World Team Cup in Dusseldorf.
Berdych broke the normally dominant Roddick serve four times as he blazed to a 6-1 6-2 victory, while team-mate Radek Stepanek beat James Blake 6-2 6-1 to give the Czech Republic an unassailable 2-0 lead over the USA in Red Group.
The doubles rubber will be played on Wednesday.
Serbia ensured their second straight win in Blue Group as Janko Tipsarevic and Viktor Troicki overcame Russia's Alex Bogomolov and Dmitry Tursunov respectively to put them 2-0 ahead.
Tipsarevic set the Serbians - who had beaten Croatia in their opening match - en route to victory by beating Bogomolov 6-1 6-3, and Troicki was also a straight-sets winner, 6-3 6-2.
Germany nudged ahead against Croatia after Florian Mayer's emphatic 6-1 6-1 win over Ivan Dodig, and Argentina hold the overnight lead against Japan after Leonardo Mayer beat Tatsuma Ito 6-4 6-4.
