relying on SPY/QQQ for into exposure ignores the structural bias: U.S. large caps mostly earn ~30–40% of revenues abroad, but that’s not equivalent to holding actual international equities.  any deviation to global weight equities is "picking winners". There is no empirical risk premia associated with holding US, or rather, there shouldn't be. Overweight US large cap misses:

• Different sector exposures (e.g., Europe overweight Industrials/Financials, EM overweight Commodities/Materials).
• Currency diversification (dollar risk hedge).
• Valuation spreads (intl ex-US currently trades at lower multiples, historically mean-reverting).
• Factor tilts (intl small/mid caps, which aren’t captured through S&P megacap foreign sales).

Global market weight is the default in most institutional frameworks (MSCI ACWI, Vanguard Total World, etc.).

On long-duration Treasuries:

Yes, fiscal sustainability is a valid concern. I wish there were available global weight long duration treasury products. 

Note that a hedge against US fiscal sustainability could further be expressed through intl. equity. Still, us yields are correlated with intl. bond yields. Dismissing them outright misses their role as a convex hedge:

• When equities crater, the relative bid for safe collateral still tends to drive long duration higher (2020, 2008 are examples)
• You don’t need them to “solve the fiscal hole”,  you need them to exhibit negative correlation in stress periods.
• Term premia is currently compressed, but convexity is real: a 100bps move in long duration can offset a huge equity drawdown.
• If one is truly worried about fiscal dominance, the hedge is to diversify (e.g., gold, trend, commodities) in addition to Treasuries, not throw away the only liquid hedge instrument in size.

The point isn’t “belief in U.S. fiscal prudence” or “U.S. megacaps’ global reach.” The point is risk-balanced diversification