crg

Argentina and Uruguay were kicked off with people in the air on their way to the US because their economies tanked. It would be odd to put them back on considering Argentina may default.

tht

I would look here for the most accurate information, I know from experience an onward ticket is fine, e.g. if you have a round the world ticket, you can go UK-US-NZ/AUS/Asia etc for as long as you want on your trip, just not to US and adjoining countries. The main point here is what they think your intent is, if they think you are planning to back-to-back 2 90 day trips you may get turned away. An once that happens no more Visa Waiver, and getting a B2 will be harder.

If you have 6 months off, I would suggest doing 80 days in US (to be safe) and then flying on somewhere else to do some travel.

Visa Waiver Program & ESTA | Embassy of the United States

A few FAQ's that may help:

If I enter the United States visa free under the Visa Waiver Program, can I then travel to Canada/Mexico/ Bermuda or the islands in the Caribbean?

Yes, provided you have a return or onward ticket. If your return journey will take you back through the United States, even if only in transit, the total trip, including both periods of time spent in the United States/Canada/Mexico Bermuda, or the islands in the Caribbean cannot exceed 90 days. If it does, you will require a visa.


What if I want to stay in Mexico, Canada, Bermuda or the islands of the Caribbean?

If your ticket terminates in Mexico, Canada, Bermuda or the islands of the Caribbean, you must be a legal resident of the area in order to qualify for visa free travel. If you are not and your stay will extend beyond 90 days from the date on which you first entered the United States, you will require a visa. Legal Permanent residents include diplomats, students or temporary workers at companies located in these areas.


If I am transiting through the United States to Mexico, Canada, Bermuda or the islands in the Caribbean under the Visa Waiver Program, does the 90 day period begin on my initial entry into the United States, even though I am there for only a couple of hours?

The regulations are the same as if you entered the United States for a holiday. If you will transit the United States to Mexico, Canada, Bermuda or the islands of the Caribbean the total trip, including both periods of time spent in the United States, Canada/Mexico, Bermuda, or the Caribbean islands cannot exceed 90 days. If it does, you will require a visa, unless you are a legal permanent resident of the country.