Well I am pretty confident about the AMS-EWR-LAS 70 minute connection since the customs should be in Terminal C. The last 3 times it took all but 12-18 minutes from deplanig to beeing in the C concourse.
A lot of times when they take of on time we have been 30-40 minutes EARLY since the timetable is so padded.
If all goes wrong, there is a later flight to LAS too.

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Viele Grüße

Oliver