I suspect part of the problem is that the US doesn’t currently have a light tank/tank destroyer solution (which the US Army is actually presently looking for) and the Abrams isn’t actually all that air- or sea-mobile as modern versions of it are **74 tons**. Getting the M1A2C/D to the beach is going to consume a lot of sea or airlift that could be used for more vehicles and troops.
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Sherman tanks were used in the Pacific Theater...Obviously, Sherman tanks were not very heavy...
I thought about M551 tank...But, that light tank is no longer in service...
The 551 was an utter death trap, especially when it hit a mine. It had (essentially) caseless ammunition sitting out in the open in the fighting compartment and when hit the thing would just go up.
Saving myself typing by linking a prior post on a similar subject: http://www.freerepublic.com/focus/f-chat/3604214/posts?page=25#25