Well we'll see, AMZ have been in previous trouble for creating monopolies of industry (which they actually won in the end though) but it is very likely it could happen in the future.
But you are right about America, but Amazon operates worldwide and if it costs jobs (we are talking 100,000-1,000,000's of jobs) the European union will step in for Amazon Europe S.A.R.L, as they have done before with plenty of industries.
But in regards to your comments about tech is growning, we just need to adjust - you are right but we need a transitional period regardless. Tech makes things more efficient. As efficiency increases, labour needed decreases. When labour decreases, so do jobs. Unemployment then has a knock on affect to the economy. So adjusting needs to be monitored closely.
If 90% of people at McD and Walmart got laid off, that is about 2.4 million people without a job.