Iceland and the UK in particular. They wouldn't even let me in at London Heathrow without a printed out return ticket (I had to run over to the British Airways desk to get a copy).
Either way - I was not allowed to stay longer than a few weeks.
That's not a wrong thing, it's very normal. If you want to stay, you have to apply for residency.
By 1) relying on such labour and 2) denying either lawful entry or any plausible path to permanent status for the vast majority of these workers and their families, not to mention many, many, many broken promises along the way (asylum, DREAM Act, don't get me started on Native American treaties), the U.S. has de facto maintained a legally-underprivileged and disadvantaged working class long after the statutory prohibition of (most) slavery and indentured servitude.
Yes, there are also economic and political circumstances within the US geopolitical orbit which encourage inward migration. That too cannot be separated from long-standing U.S. foreign, economic, and military policies within the region.
This needs to stop.