AMS Baggage Claim and Connecting Flight to Milan

As this is two separate bookings, I would say 1 h 40 is not feasable.
You would need to go through immigration (passport control) and pick up your luggage. This could take one hour or more.
You then need to "bag drop" with Easyjet (you must check in online and print out your boarding pass ahead of time) and get through security. To quote EasyJet: "easyJet check-in desks close 40 minutes before the scheduled departure time of all flights. .... easyJet recommends that passengers check-in two hours before the scheduled departure time".
And you have to allow contingency for your flight to Schiphol landing late.
CONCLUSION: No way can you do 1h40 transfer into an Easyjet flight.

@Carol
If you are checking bags on your Seattle flight 1 hour 40 minutes isn't enough time. Discount airlines don't handle baggage transfers from other airlines. So you will need to go through immigration, pick up your bags from the carousel, exit the terminal through customs, reenter the terminal, checkin at the EJ desk, go through immigration again, then through a security checkpoint, and then to your Easyjet gate.
Also be aware that if your flight from Seattle is held up and you miss your Easyjet flight for any reason those tickets are worthless, and you will have to pay big bucks for a last minute fare to Genoa.

If it were me I would do a transfer to Genoa via the Seattle airline's partners on one itinerary, even if it costs a bit more, the journey will have a lot less hassle.

Agree with the others. We recently missed a connection in AMS. Several little things. Arrived earlier, gate not available, then 20 minutes late to the gate. Made the mistake without thinking of sitting is the far back corner of the plane. Nearly the last ones off. Lost another 25 minutes. Long lines at immigrations although they were permitting people with short connections to use a special line. Another 20 gone and the same for security on the next flight. Another 20 minutes. Stopped to take a picture of airport interior - 3 to 5 mins. That was the killer. The next gate was downstairs and further than we had anticipated. Maybe another 15 minutes or so. We arrived at the gate 15 minutes prior to departure and noticed, as we walked up, that a bus was pulling away and no one but one gate attendant was in the area. The gate closed 15 minutes prior to departure because people were being bused to the plane sitting on the tarmac some distance from the terminal. If we hadn't stopped to take a picture we would have made it.

This is one time I think it would be smart to fly directly to Milan.

PS I was sure your were looking at direct flights to AMS so most out of curiosity I looked to see what other options were available in mid May. I was surprise to see it was almost $300 cheaper to fly directly to Milan via a New York connection. While I prefer a direct flight also, there are times when I can live with a connection that is convenient and cheaper.

Delta, KLM, & Air France are flying partners.

How are the flights if you fly to the East coast (New York, Newark, Washington D.C., Atlanta) & pick up a flight straight to Milan?

Or
1) SEA to AMS (KLM) to Milan
2). SEA to CDG (Air France) to Milan

If those flights exist.

I am with the others in suggesting you fly KLM/Delta to Milan. I just did the reverse in October checking my bags thru from Milan Linate to my home airport in Idaho. Have you already bought the SEA - AMS ticket?

If you do decide to do an EasyJet flight, do be aware that the EasyJet luggage regulations are very different from Delta/KLM so even if something is OK to carry on for your SEA - AMS leg it may not be Ok for EasyJet. If you've not flown with a budget carrier in Europe before, study their rules very carefully before you buy. I recommend buying up and paying to check luggage, to pick your seat and have Speedy Boarding.

BTW, I prefer doing the Seattle - AMS flight and changing there rather than having to change planes on the East Coast.

If Delta will still allow you to add a connection either Milan or Genoa on the same ticket, then I would do it. Whether you pay with cash or miles, the price is usually not much different, and the connection becomes much easier. If you don't have that option, then plan on the longer layover before catching EasyJet; or you could spend a night in Amsterdam and make your connection the next day.