Is the tap water safe to drink in Argentina?

Also, do they serve it in restaurants like the do in the US? Or do they use bottled water?

Yes, it is safe to drink. In restaurants, if you order water from the menu, it has a price and it is bottled. If it's free, it's tap water.
If you happen to go to some areas in the northern provinces where the water may not be safe to drink, you will be informed so and you will not be given it, there's nothing to worry about.

Yes, it is safe in the central regions (e.g. Buenos Aires and the surrounding provinces and other well-populated areas). Argentina is a very modern country. However, the outer provinces like where the Iguazu Falls is and down in Patagonia are a little iffier. Stick with bottled water there. And the restaurants will serve tap unless you ask otherwise.

I was just in Patagonia and the restaurants served ONLY bottled water. They bring a cold bottle to the table and open it in front of your eyes. No ice. You have your choice between water (sin gaseosa) and carbonated water (con gaseosa). Also, beer is costs just a bit more...

Water is safe in Argentina! All way around! Plus you have several choices of "real natural spring water"

Not to worry!

By the way, enjoy the excellent wine!

yeah!, it's safe...and if you are gonna pay the water, they'll give a bottle...but, if you just enter a bar to ask for water to drink, they'll give you tap water...

Yes it is perfectly ok to drink water in argentina from the tap. I go to argentina all the time and I drink plenty of tap and I am just fine. Typically restaurants will offer water but beware that if you do not tell them that you want regular water with no gas they will assume that you want carbonated water. But also enjoy other argentinean drinks not just water. Maybe a quilmes some wine or an argentine coke.