When, why and how did Americans lose the ability to politically organize?

In Irish politics, the Republican movement to return a piece of land the size of Essex County has been able to exert a lasting, intergenerational presence of gunmen, poets, financiers, brilliant musicians, sportsmen all woven into the fabric of civil life. At one point, everyday farmers were able to go toe-to-toe with the SAS, conduct international bombings across continents and mobilize millions of people all over the planet. Today, bands singing Republican songs about events from 50+ years ago remain widely popular. The Wolfe Tones for example were still headlining large festivals 60 years after they founded.

20th century Ireland was a nation with very little. Depopulated and impoverished, but nevertheless it was able to build a political movement without any real equivalent elsewhere in the West.

In Modern America, the worlds richest and most armed country, what is alleged to be a corporate coup and impending fascism is met with... protests at car dealerships and attacks on vehicles for their branding. American political mass mobilization is rare, maybe once generationally, and never with broader goals beyond a specific issue such as the Iraq War or George Floyd. It's ephemeral, topical to one specific stressor and largely pointless. Luigi Mangione was met with such applause in large part, in my view, because many clearly wish there was some or any form of real political movement in the country to participate in. And yet, the political infrastructure to exert any meaningful pressure towards any goal with seriousness remains completely undeveloped and considered a fools errand to even attempt to construct.

What politics we do have are widely acknowledged - by everyone - to be kayfabe. Instead of movements, our main concept is lone actors, individuals with psychiatric problems whom write manifestos shortly before a brief murder spree. Uncle Ted, Dorner, now Luigi and more.

This was not always the case. In the 30s they had to call in the army to crush miner's strikes. Several Irish Republican songs are appropriations of American ones from before the loss of mass organization. This Land is Your Land, We Shall Overcome, etc. The puzzling thing is that the Republicans still sing together while we bowl alone.

When, why and how did this happen? Is it the isolation of vehicle dependency? The two party system?