An officially imported, USA camera for "full price" will have at least a 1 or 2 year warranty against any sort of failure of camera or lens (longer warranty may be available to purchase at added cost).

Undoubtedly a camera shipped to you from Hong Kong (or elsewhere overseas) at a significantly lower price will be "gray market". Gray market basically means it was imported unofficially, not through the manufacturer and their USA/N. American distributor "official" channels.

An unofficially imported or "gray market" camera will have no "official" warranty at all. As a result there's some risk buying that way, although most modern gear is pretty darned reliable. I think the majority of "problems" you see are actually "user errors", no fault of the gear. Even so, there's at least some risk that a failure could occur.

With Canon, you can get an imported camera repaired at their facilities, at your expense. You also can get it repaired at an independent shop, if it's not beyond their capabilities. If spare parts are needed, Canon will sell them to an independent shop (or to you directly).

With Nikon it's another story. Nikon USA refuses to work on import/gray market cameras. Further, they will not sell spare parts to independent shops. So if any parts are needed for a repair, you are out of luck. Unless you can find someone who can repair it with parts from another "donor" camera or an overseas repairer who has access to parts, you might as well toss a failed, gray market Nikon in the trash. It's just a paperweight or Christmas tree ornament now.

I don't know anything about repair/parts policies of the other manufacturers.

When it comes to the cameras themselves, they are basically the same, regardless. AFAIK, Nikon uses the same model names throughout the world.

Canon for some reason continues to use different model names in three markets: N. America (Rebel SL2, for example), Japan (Kiss X8 = SL2) and the rest of the world (EOS 200D = SL2). So the nameplate on a Canon may be different, depending upon the source. But there's no functional difference in the cameras themselves. In very few cases, Canon has only offered a model in one market or another... but that's not common (I forget which, but there was an earlier M-series "mirrorless" that was only offered in Japan.)

Personally, I'd be verrrrrry nervous buying a "daily user" camera off eBay from overseas (I have bought vintage collectible cameras that way, though). I'd also worry about buying from Amazon "partners" in unknown locations (Amazon direct, where they warrant it, no problem... also some of the major retailer/partners who sell through Amazon). Little to no recourse if there are any problems.

In contrast, if you buy a gray market/import from a well established, major US dealer, you at least have recourse if something goes wrong initially. Most modern electronic camera gear, if anything is wrong with them it happens right away and is apparent right out of the box. If it works correctly for a few days or a week, it will very probably have a long, happy, trouble-free life. The major, well-established, domestic retailers typically offer a 14 day, no questions asked right of return on gray/import items and used gear. They might additionally offer a "store warranty" for a longer period of time.

General rule of thumb... beware if the price is significantly below that of the really big, high volume stores like Adorama and B&H. Prices very much lower than they can offer are likely only possible by taking away something (warranty) or by substituting a cheaper item. In the worst cases, it's a bait n switch scheme where after you place the order they'll call you to sell you the battery and charger or something else essential, at a much higher price... and you actually end up paying more total, for what's normally included in the box from the more reputable stores!

SL2 is often sold with EF-S 18-55mm IS STM lens... which is plasticky, but capable with auto focus that's quieter, smoother and faster than the AF of the cheaper "micro motor" EF-S 18-55mm IS II.

Some retailers bundle the SL2 in a two lens kit... with the above 18-55mm STM, and the EF-S 55-250mm IS STM. That's a decent lens too.

Costco (and perhaps some others) instead offers a three lens kit with the SL2 that instead adds the EF 75-300mm III, which I'd recommend avoiding. It's Canon's cheapest telephoto zoom, has not got as good image quality, has slower/noisier micro motor focus drive, and lacks image stabilization... The 55-250mm IS STM is a better lens in pretty much all respects. The third lens Costco includes is the EF 50mm f/1.8 STM, which is a decent little prime (i.e., not a zoom) and, among other things, nice for portraiture when it's used on an APS-C camera like the SL2.