Is 1 hr enough time in Amsterdam for a connection going from Venice to US?

There are probably about 10 questions to be asked before anyone can answer that.

For starters:

What if your first plane is late?
Can you check your luggage through without reclaiming it?
Is it one or two airlines?
Is it a connection booked by a single airline?

It is a legal KLM connection. Both planes KLM.

I wouldn't risk it...in any case.

I believe you will have to go through passport control as you will be leaving Schengen. Plus you will have to go through security again. An hour is barely enough time, and you can't guarantee the flight from Venice will be on time. It isn't worth risking it, nor is it worth the worry you will experience if your flight is a few minute delayed.