The issue is not Germany providing tanks, they are preventing others from doing so. Other countries (Poland, Spain, and others) have agreed to transfer their Leopard 2 tanks to Ukraine. Problem is because there's an export control agreement with Germany, Germany has to give permission to the other countries to transfer their tanks.

View is that a couple hundred capable tanks are being held up by Germany.

Britain has offered up some Challenger 2 tanks but there's not as many.

US has a ton of M1 Abrams but logistics are more difficult due to them using turbine engines and running on jet fuel instead of diesel.

Abrams tanks have turbine engines using a very different fuel than all of the other vehicles Ukraine is using. Essentially Jet Fuel vs Diesel fuel. Leopard 2 tanks use diesel.