It is, but Chobham is severely overrated, and even defeated by RPG's one *multiple* occasions. - The M1 technically has a "worsened" variant of it compared with the Chally 2. I thought the T-90 didn't have a hard-kill APS.... - It was discussed in a different thread.
There is Chobham armour as used on the Challenger I and Abrams, and there is second generation Chobham, which is often called Dorchester armour used in Challenger II and later model Abrams... and no it is not perfect and needs to be made in fairly thick heavy layers to be effective.
BTW The Abrams and Challenger and Leclerc don't have hard kill APS systems... the T-90s systems were developed but not deemed necessary.
At the end of the day the protection levels are quite comparable for Russian and western tanks... roughly 1.2m for HEAT and 900-1,000mm for kinetic from the front.