Two got spooked and were nervous about their future with only 13 months tenure. The third is a senior dev with more than 10 years who’s disgruntled and convinced he’d only be kept on to tidy up loose ends and then discarded. Of the remaining engineers some have 18 months tenure and others 8 years.

Their concerns are valid. If I was them I'd leave as soon as I had an offer from another company. A company opening positions in another location with such few employees is very concerning.

Assurance that their jobs are safe is a joke. Its like when a company says that they are just one big family. Only management believe those lies and they force them on everyone else.

The company could put their money where their mouth is.

Are you truly being honest about keeping them on? Write up a contract that guarantees them X years of employment, at Y severance per month if terminated early.

More realistically, you should consider that the ones resigning have a better read on the situation than you do.

To look at the bigger picture here, this is really the longtail of trust lost in companies due to excessive layoffs and clear consistent messaging that the employee is just a head that can roll when its convenient and cost effective.

The reaction of those 3 employees was my own, and when the culture is so clearly against you, and the company clearly doesnt have more than fluff words (across the org) to retain you, then the net sentiment has shifted strongly away from "trust the employer" to "the employer will screw me the first chance they get".

The guys may be scared or disgruntled. But they very well could be making assumptions that line up with reality. Even you may not be privy to the long term plans for AUS. It may be a temporary stay until product knowledge is well established in the USA.