targeted boycotts seem to prove more effective in the United States

Targeted boycotts have never removed a party from power. There has never been a general strike in the US either. But general strikes in other countries have been effective. I can't think of anywhere that boycotts have accomplished much unless they've been accompanied by mass action.

I can’t be sure, having never seen general strikes manifest or boycotts that lasted.

Look outside the US. US labor law has been rigged to prevent unions having any power, and the US has always sucked at worker solidarity (except for some sporadic outbreaks of rebellion in the early 20th century before the IWW was suppressed).

Boycotts also rule out those of us who live in poverty who can’t afford to have opinions.

The swadeshi movement organized by Gandhi largely involved poor people resisting exploitation by state monopolies. It was pretty effective, though the boycott was only one part of a much broader strategy. The same could be said about the Montgomery bus boycott, though the goals of the SCLC were narrower than regime change (when King tried broadening it to something that looked a bit more social-democatic and applicable to all working Americans, he caught a bullet). Same thing happened to Fred Hampton when he proved effective at building alliances that defied the prevailing racially based divide-and-rule scheme. The elite really doesn't want us showing solidarity.

For a General Strike to work, there does need to be a somewhat unified vision of what the strike is against. That means getting workers educated about the situation as much as possible.

A boycott can sometimes work against individual corporations, but a boycott to make the government listen would require sustained participation from a massive section of the population, which seems unlikely to say the least. In contrast, a general strike only needs workers in critical unionized industries to join in to cause a virtual halt of economic activity (dock workers, train workers, truckers, etc). This lowers the numbers needed to be effective by an order of magnitude, and is thus much more feasible. History has shown it to be the most effective non-violent tool we have for over 100 years, and so far nothing else has come close.

Prefiguration could be considered a 3rd method. Building the alternative systems we want to see and use in the world to lower our dependence on the current system facilitates the ability to enact general strikes, boycotts, and reduces the leverage they have over us to not enact resistance.

A fourth method would be perhaps more extreme, like collectively destroying all of the world's databases that contain financial debt records, Fightclub/Mr.Robot style. But that would require extreme coordination between established capable groups, and currently is not a feasible option.