Right now It is possible to get a direct flight from the States to Quebec city if you are coming from Newark, Philadelphia, Chicago, Miami and Fort Lauderdale.
This is Quebec city airport official website : https://www.aeroportdequebec.com/en
Travelling to Quebec city I always prefer Westjet. They do offer some direct flight but you could also connect from another Canadian ariport. You don't have to go through Montreal when coming to Quebec. Check other Canadian cities like Toronto or either one of the American airport from above. For exemple you could fligh to Newark with American Airlines and from there to Quebec city with Westjet.
Flight between Montreal and Quebec can be as expensive as going to New York so it is worth doing research first.
I am suggesting Westjet because I had very good experiences with them : https://www.westjet.com/book/
My personal rule is if there is a difference of 100$ or less between flying to Quebec city or to Montreal I go for Quebec (I live in Quebec but sometimes there are more than 200$ difference between the two in this case I chose Montreal).
A round trip from Montreal to Quebec city will take around 3 hours and cost you around 80$.