US weaponisation of frontier-AI access (model export controls, foreign-national lockouts) is fragmenting the global AI stack along security lines, prompting allies to seek sovereign alternatives. Distinct from the valuation/capex exceptionalism leg: this is a geopolitical-access channel that could redirect AI capex flows and reshape semiconductor/cloud supply chains. Bears on ES (US AI incumbents' addressable market) and the broader tech-supply-chain complex.