It seems most of the world is moving towards ERTMS. The 'not-invented-here' syndrome is strong in the US. But there may also be compatibility issues, in the US

It seems most of the world is moving towards ERTMS. The 'not-invented-here' syndrome is strong in the US. But there may also be compatibility issues, in the US they have a completely different view of railroad safety (laregly boils down to 'if there's an accident, our trains should be built like tanks so it doesn't matter' vs 'there should never be railroad accidents'). That's one of the reasons why there is very little transit on main lines.