Reference:
https://docs.microsoft.com/en-us/azure/traffic-manager/traffic-manager-nested-profiles Traffic from West Europe:
Basedd on TM1 table, West Europe will trigger TM2. However, as the MinChildEndpoint is set to 2, and App4 is degraded (down), the entire TM2 will not be considered available.
This goes back to the origin TM1 that uses performance traffic-routing method, which means the closest location is App1 and naturally be the next best performance instance.
Hence, Answer = App1
Traffic from West US:
Based on TM1 table, West US will trigger TM3. However, both App2 and App6 were degraded (down), so none of them can be considered.
This goes back to the original TM1 that uses performance traffic-routing method, from TM1, the other 2 US locations would be App2 and App3. But App2 we know it's already degraded (unavailable), hence the only option would be App3.
Answer = App3