Go to a fiambreria and ask for panceta ahumada (smoked). Ask them to cut it thick (you have to show them with your fingers - most of the time they will cut a slice and hold it up to show you if they got it right) or you will get deli-ham-sliced thickness, which is very difficult to cook right.
Alternatively, you can sometimes find special cuts of smoked panceta in the supermarket, depending on whether they've ordered it that week or not, or whether their request has been filled by their suppliers, etc. I can't remember the brand that I've found best, but it actually uses the word "bacon" if I remember correctly (though not available very often). Campo Austral often has 2 piece packages for sale as well, but they are cut a bit too thick for my taste, although it does in a pinch (and makes great BLTs!) and is almost always available. Both of these items are found with the pre-packaged lunch meats and cheeses (fiambres) in the supermarkets.
With either of the two options above, I like to soak my panceta in water mixed with a lot of liquid smoke and some salt and sometimes some black pepper. Put it in a tupperware in the fridge overnight (or a few hours at least) and then let it dry the following day on paper towels. It's still not exactly like US bacon, but it comes closer than if you cook the panceta directly, which still isn't bad - I've started cooking it directly from the package more often than soaking it lately because of the bother.
But to me, the biggest key is to get them to cut it thick or buy the right package in the super that's thick enough.
I also like to make sausage patties out of chorizos - strip the outer skin to get just the meat, mix with salt and black pepper and maybe some garlic (or whatever you prefer) and then form into patties. Not as good as I remember something Jimmie Dean, but not bad either...
As far as where to get an American-style eggs and bacon breakfast - the only place I've heard of that wasn't mentioned here was hotel Palacio Alvear on the corner of Alvear and Ayacucho. I think they only do a Sunday brunch there as an American-style breakfast. I've never been, though I live about 4 blocks from it. I hear it's very good and quite expensive.