Sean Longstaff fired the visitors ahead in the first half at Vicarage Road, but in-form Hornets ace Ismaila Sarr equalised in the 72nd minute.
Newcastle had more shots and more shots on target than their hosts, but they failed to capitalise in the absence of striker Callum Wilson, who is out until next month with a thigh injury.
Bruce admits his side should have been “out of sight” on their way to a first league win of the season prior to Sarr’s strike.
“The game should have been put out of sight but you can’t come here and dominate the way we did and create the chances we had and miss them,” Bruce told BBC Match of the Day .
“We nearly got punished for it at the end, which would have been totally unjust in my opinion. Our performance was terrific, we’ve done okay of late and haven’t managed to get that first win.”
The Magpies boss added: “We were sloppy on too many occasions. The hardest part of the game is to score a goal, and that is a bit of mentality; you’ve got to go cold in front of goal.
“We’ve played very well and should have come here and won the game comprehensively.”
Newcastle have begun the season with three draws and three defeats, while they exited the Carabao Cup at the second round with a penalty shootout defeat by Burnley.
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Bruce’s claims about Newcastle’s wastefulness were echoed by midfielder Longstaff, who rifled the visitors ahead in the 23rd minute.
“In the first half alone we should have been three or four goals in front,” said Longstaff. “We had a lot of very good chances, more than we’ll create in most games and it is very disappointing to come away with a point.
“We were excellent in the first half and we really dominated the game.
“It was the best we’ve played this season. In the second half, their fans were up and they were in the game, but we were creating much better chances. It is a disappointing day.”
Up next for Newcastle is a trip to Wolverhampton Wanderers early next month followed by a home encounter with Tottenham Hotspur after the October international break.
The Magpies will hope to have Wilson available for the clash with Spurs, while playmaker Jonjo Shelvey, goalkeeper Martin Dubravka and defender Jamaal Lascelles could also return from injury.