As expected, Czech sixth seed Berdych made light work of Lleyton Hewitt with a 6-3 6-4 6-3 victory in the first round.
The powerful and aggressive Berdych hit 43 winners and was largely untroubled by the veteran Australian at Flushing Meadows.
With Novak Djokovic in scratchy form and Roger Federer beatable, Berdych and Dimitrov are among those capable of challenging at the final grand slam of the year.
Dimitrov, the Bulgarian seventh seed, was impressive as he disposed of American Ryan Harrison 6-2 7-6 (7-4) 6-2.
Wimbledon semi-finalist Dimitrov hit 37 winners and just 19 unforced errors in a good display first-up.
Stanislas Wawrinka fought off a gritty Thomaz Bellucci to win their second-round clash.
The Swiss third seed went from impressive to battling as he claimed a 6-3 6-4 3-6 7-6 (7-1) victory over Brazil's Bellucci.
It proved to be a day of retirements in the men's draw.
Croatian 14th seed Marin Cilic led Marcos Baghdatis 6-3 3-1 when the unpredictable Cypriot retired.
Feliciano Lopez, the Spanish 19th seed, was locked in a battle with Ivan Dodig when the Croatian retired at 1-1 in the fifth set.
American Steve Johnson suffered severe cramping and retired when leading Japan's Tatsuma Ito 2-6 6-3 7-5 1-4.
Latvian 11th seed Ernests Gulbis thrashed Frenchman Kenny De Schepper 6-1 6-4 6-2.
Big-serving South African Kevin Anderson, the 18th seed, sent down 29 aces as he fought his way past Uruguayan Pablo Cuevas 6-3 6-7 (3-7) 4-6 6-2 7-6 (7-1).
Poland's Jerzy Janowicz was too good for Serbian Dusan Lajovic in a 6-3 7-5 5-7 7-5 win and Portuguese 32nd seed Joao Sousa edged Canadian Frank Dancevic 7-6 (8-6) 3-6 6-2 4-6 7-6 (7-2).
Russian Teymuraz Gabashvili beat Colombian 27th seed Santiago Giraldo 6-3 1-6 7-6 (8-6) 6-3.
Israel's Dudi Sela recovered from a slow start in a 1-6 6-3 6-2 7-5 win over Argentine Carlos Berlocq and Alexander Kudryavtsev won an all-Russian affair against Evgeny Donskoy 2-6 7-6 (8-6) 3-6 6-3 6-4.
Slovak Martin Klizan beat Belgian Steve Darcis 3-6 2-6 7-6 (7-5) 7-5 6-4 and the in-form David Goffin crushed Niels Desein 6-1 6-3 6-3.
Austrian Dominic Thiem was too good for Slovakia's Lukas Lacko 6-3 6-3 6-2 and Ukrainian Illya Marchenko overcame Switzerland's Marco Chiudinelli 7-6 (7-3) 4-6 7-6 (15-13) 7-6 (7-4).
Facing Wawrinka in the third round is Slovenian Blaz Kavcic, who upset French 30th seed Jeremy Chardy 6-2 7-6 (8-6) 6-3.