Hmm, what was the last time someone succesfully assassinated a US Ambassador?
link
Adolph Dubs-1979 Afghanistan killed during a kidnapping attempt by leftists
Francis E. Meloy, Jr.-1976 Lebanon killed by Palestinians
Rodger Davies-1974 Cypress killed by Greek Cypriots
Cleo A. Noel, Jr.-1973 Sudan killed by Palestinians
John Gordon Mein-1968 Guatemala killed by Commies
Almost a trend there.
There's no trend at all. Besides the 70s having a higher occurrence.
It's also notable those are mostly left wing groups or secular Palestinians.