If it is American, it is likely to be simple. I negate Setters of Catan, jerks of “A Card Laid of a Card Played” and those who absolutely will not help newcomers make Catan murder, especially adding expansions. If you get nice people, ok but if you get overly nice people, it is really bad. The robber will be thrown back in the box, the resources will dry up because of that, trading will occur, monopolies start, friendship pacts start, snacks are offered, winning game circumstances COULD show up (the palace) and meals bargained will not be paid for because no one has the money to buy you that food and you’ve traded away your snacks to other players while gaming.
Candyland and other games that perturb the colourblind are simple. There was an old garfield game that if you bought a standard set of dice you could have a laugh riot with! Garfield, with the aid of lasangas, has to make it 3 times around the track, getting gold rings on his tail each time. Using different dice, see how fast you can move him. I rolled a seven 0007 on Thousand Hundred Ten One Dice. Racing games sometimes come with their own dice. They teach kids to count.
There is a Munchkin flowchart. It can be hard to locate the good one because there a two original versions out there. This makes Munchkin games simple. Also I am not a MIB anymore, Steve Jackson Games are fairly simple and Cthulhu dice (die really) is cheap and easy. Zombie dice is way easy there are instructions and bringing them to a restaurant to waste time while waiting is GREAT.
I especially like, make this my one suggestion, Carcasonne is a tile laying game and except for analyzing the map for properties and adding extensions (that don’t need to be in order) it is simple but don’t play with someone who thinks it is funny to run the game off the table. There should be a “on the table only, no reworking” rule to the game. No little satellite cities. Start with the river.