I'm not sure about the FIRE crowd, but the crowd at Bogleheads.org advocates a three-fund portfolio with the equity side being composed of a 60% allocation to U

I'm not sure about the FIRE crowd, but the crowd at Bogleheads.org advocates a three-fund portfolio with the equity side being composed of a 60% allocation to US equity, 40% ex-US equity (exact ratio up to the individual to decide). This diversification tries to address the risk you brought up of being over-concentrated in your country's stock were something like Japan's stagnation from 1990-present to happen to the US.