Great karts and well supported by Italian Motors (which basically is Italkart). Definitely competitive with anything else out there. You didn’t say whether you are looking to buy new or used. My 2008 is still solid, rust free and straight as an arrow despite some, errrr, “interesting” driver errors that occasionally turn it into a lawn mower. The only chassis part that has ever broken is a tab on one of the seat stays, which was fixed with a $60 welding job.
As for “local” support, the fact is that most kart chassis parts which you might actually break or need to replace (eg., axles, bearings, brake seals, side pods) are interchangeable and/or off-the shelf stuff. And Italian Motors has free (!) shipping for web orders.
Engine parts are something else, but you can put any engine on an Italkart that you can put on, say, a CRG. I’d be more worried that my engine had local support than that my chassis did.