For anyone curious, The Tank Museum has a "Tank Chat" (YouTube) on the Leopard 2.

Notably, it can use the same ammo as the Abrams and it gets about the same average MPG as the Abrams (.57 vs .6). Both come out of joint US-German development on the MBT-70 in the 60s and 70s.

I suspect part of the issue with sending M1A1s to Ukraine is that there's a lot of gear on it that are still top secret - so that either needs to be declassified somehow, or removed and replaced with non-classified but probably less capable gear that serves the same purpose. As well, there isn’t an Abrams repair depot in Europe and one needs to be built (Germany? Poland?).

Also, as I've mentioned, the M1A1 can run on diesel (jet fuel is basically better-filtered diesel without cetane booster) or even gasoline in a pinch, although, I'd expect that'd shorten turbine life.