when can we say that workers are alienated from their work from their fellow workers
Marx's theory of alienation Capitalism reduces the labour of the worker to a commercial commodity that can be traded in the competitive labour-market, rather than as a constructive socio-economic activity that is part of the collective common effort performed for personal survival and the betterment of society. In a capitalist economy, the businesses who own the means of production establish a competitive labour-market meant to extract from the worker as much labour (value) as possible in the form of capital. The capitalist economy's arrangement of the relations of production provokes social conflict by pitting worker against worker in a competition for "higher wages", thereby alienating them from their mutual economic interests; the effect is a false consciousness, which is a form of ideological control exercised by the capitalist bourgeoisie through its cultural hegemony. Furthermore, in the capitalist mode of production the philosophic collusion of religion in justifying the relations of production facilitates the realization and then worsens the alienation (Entfremdung) of the worker from their humanity; it is a socio-economic role independent of religion being "the opiate of the masses".[3]
Deindustrialisation by country In the United States, deindustrialisation is mostly a regional phenomenon, centred on the Rust Belt of the original industrial centres from New England to the Great Lakes. While many Americans put the timing of industrial crisis as 1979 to 1984, in fact the most massive loss of US manufacturing jobs occurred in the 21st century: one third of US manufacturing jobs disappeared between 2001 and 2009, according to the US Bureau of Labor Statistics https://data.bls.gov/timeseries/CES3000000001.