Uh there is still "a little" machining, assembly, welding etc etc Remundo...
The M1A1 and the T80 are strictly of the same generation initially... there may be "software" upgrades on both sides... but not sure that the USA is releasing their latest technological versions into the wild with a risk of being captured by the Russians! Even though they probably already know everything...
Same for leopard 2...
The Leclerc is a more modern one...but its ammunition, gun and armor are no better than those of the other 2...
If you think that a slightly more modern tank can destroy 5 tanks of design just 10 years older (outside the world war period) I advise you to install and spend a few hours on world of tank, it's free …
The T34 was older than most panzers in Kursk…(and it is even still used in the world unlike the panzers of the time which nevertheless scared everyone…)
For the quantities produced and technical details of each of these 4 tanks see wiki…
Here I found this about the French flagship:
In 2016, the availability rate rose to 61%. Out of 241 Leclerc tanks in service, only 147 tanks are available, for a cost of maintenance in operational condition of around €20 per month