City have three home games remaining – against Brentford, Palace and Aston Villa, on the final day of the season (24 May).
Their remaining away match is at in-form Bournemouth, who City play just three days after their FA Cup final.
While City are aiming for a domestic treble, Arsenal now have a realistic chance of claiming both the Premier League and Champions League trophies.
Their European semi-final against Atletico Madrid is finely poised before Tuesday’s second leg after a 1-1 draw in the Spanish capital last week.
Arsenal’s three remaining league games are at relegation-threatened West Ham, then home to already-relegated Burnley before a final-day trip to Palace.
“I am worried for the West Ham game,” added Henry. “Like I was worried for Manchester City’s match today.”
BBC Sport pundit and former England captain Wayne Rooney, meanwhile, has predicted on his BBC podcast Arsenal will win all of their remaining league games and lift the title.
He said: “We’ve heard a lot about Arsenal cracking under pressure, but Guehi has never been in a position where he’s challenged for the Premier League, Semenyo hasn’t. And I think you’ve seen tonight might be the first sign of that.
“I think it’s Arsenal’s year. And I hope it is for Arteta’s sake. The work he’s put in over the last five years, and then against his former boss, Guardiola – if he goes and wins that title, that is huge for him.
“Arsenal are very consistent while City can be a little bit up and down. City at their best, you’re the best team in Europe.”
City, though, will be left extremely concerned by their capitulation against Everton, having gone ahead but been unable to see out the game.
January signing Guehi was culpable for the opening goal and City’s defence were sliced open time and time again – Everton should have been out of sight by the time they conceded a 97th-minute equaliser.
City fans who had left the stadium had to scramble back when Haaland scored to give their side hope, before Doku earned a point.
Guardiola looked to the positives by saying: “A really good performance. We played outstanding in the first half. Really, really good.
“In the second half, they made a step up and we maybe weren’t as aggressive and after [that] we gave away the goal.
“They came back and made it a proper English game – so, so aggressive in the duels.
“But in general, we made a really good performance.”