The Thunderbird crash was probably a genuine accident, they would be working up practising for the start of the airshow season.
They fly pretty close to the limits of their and their aircraft capabilities and sometimes unintentionally beyond with inevitable results.
The AV-8 crash in Africa seems to be due to mechanical problems as they have temporarily grounded them. Could be sabotage but equally it could be just an error by a member ground crew, dodgy fuel stocks (water sometimes gets into the fuel storage tanks on board ship or underground), or a host of other reasons.
The helo crash in the US happened close to the Mexican border and is being called a 'training accident' but there might be more to it than that considering the threat to the border at present.