Not in Chile. No one will thank you for a tip in dollars which they cannot exchange because it is too small an amount (I believe this will be true of all the countries you mention). Dollars are not used here. You should use Chilean pesos for small items and your credit card for restaurants and hotels.
It is impossible to say how much cash you will need, but take out US$100 out of an ATM and see if you need more later. You can always pay for a meal in cash if you have some left over at the end.
Taxis are not tipped in Chile but you can round up a fare. If there is no service charge on the bill, 10% is the norm.

I agree about all four countries. Dollars won't be of any use for such transactions.

assuming you live in the US, how would you feel if you received tips in Yen or Euros?

It is incredible convenient NOT to have to change dollars to whatever currency you need, but really ... think about it ...

Always cheapest best to use my no fee

www.capitalone.com Visa CC to ATM the

local currency for little things/tips

Visa CC taken widely use that for most things...

In addition to the good advice above:

Whatever you do, do NOT give anyone US coins. A few times I've seen Americans dropping quarters into a bathroom attendant's tip jar. While I don't recommend US currency at all, at least bills can be changed for a fee. Coins however are not changeable at all and they are completely worthless to the recipient.

Please make it easy for your service providers and tip in local currency.

In Buenos Aires, I believe it's perfectly OK to tip in dollar bills certain service providers, such as: hotel bellboys & maids and restaurant waiters, in touristy areas.

Street vendors may take dollar bills in very touristy areas. The rate of exchange should be about 3,80 Argentine pesos per US dollar.

In Uruguay, almost everyone takes US dollars.

Have a great time in South America.