If I use Thunderous Smite on my first attack and the target fails its saving throw and is pushed 10 feet away, can I use my extra attack against another target? Assuming I have enough movement left to get to another target or another is within reach...
As long as you have a target in reach, or have enough movement to reach another target (or the same target) then yes.
Unless an ability says otherwise, you can direct your attacks as you like, so if you have two attacks on your turn and multiple adjacent enemies, you could attack one enemy twice or two enemies once each. However, it is generally advisable to focus on a single target as killing one enemy is better than wounding two since you will receive fewer attacks back.
If I use Thunderous Smite on my first attack and the target fails its saving throw and is pushed 10 feet away, can I use my extra attack against another target? Assuming I have enough movement left to get to another target or another is within reach...
As long as you have a target in reach, or have enough movement to reach another target (or the same target) then yes.
Unless an ability says otherwise, you can direct your attacks as you like, so if you have two attacks on your turn and multiple adjacent enemies, you could attack one enemy twice or two enemies once each. However, it is generally advisable to focus on a single target as killing one enemy is better than wounding two since you will receive fewer attacks back.
That's exactly what I thought, but thanks for confirming swamp_slug!